Phone, data and eSIM in the USA

A phone from abroad can work in the USA in three ways: roaming on the home plan, a US prepaid line, or Wi-Fi alone. A US line needs an unlocked phone that passes the carrier's compatibility check. A call to 911 goes through even without one. Long stretches of road in Death Valley, Yellowstone and Denali have no signal at all.

Prices and rules below come from the carriers' and phone makers' own pages and the federal 911 rule. The National Weather Service, the National Park Service and the airports supply the rest, all read on 30 October 2026. T-Mobile's and AT&T's pages were read the same day from a US connection. The Federal Communications Commission's site refused our connection, which is why some answers here are shorter than you might expect.

Will a phone bought abroad work on a US network?

A phone bought abroad works on a US prepaid plan only if it is unlocked and the network accepts it. Verizon's compatibility checker asks for the phone's 15-digit IMEI, which you can show by dialling *#06#. The checker refuses a phone that is "locked by another carrier" and one that is not compatible with its network.

Apple puts the same condition plainly for an iPhone that takes another carrier's eSIM: it cannot be locked to a carrier. On an iPhone, open Settings, then General, then About. An unlocked phone shows "No SIM Restrictions" next to Carrier Lock.

Apple lists the iPhone XS, XS Max, XR and later models for eSIM, and the phone must be on Wi-Fi or a hotspot to add one. Apple also tells travellers to check the phone's cellular band support for the country. It publishes no US band list on that page.

An older phone can fail for another reason. Verizon decommissioned its CDMA network on 3 January 2023. A 3G phone, or a 4G phone without VoLTE, no longer makes or receives calls or texts, or uses data, on Verizon's network. Verizon's prepaid notice includes 911 calls in what stopped working. We could not read AT&T's or T-Mobile's notices on their own networks.

Which US carriers sell a prepaid eSIM to visitors?

All three national networks sell a prepaid eSIM to visitors on their own pages: T-Mobile's US Pass, eSIM by AT&T and Verizon's prepaid eSIM. Apple's support page on eSIM in the United States lists the carriers that "support eSIM activation on prepaid plans for international travelers". Those are AT&T, Cricket, Metro by T-Mobile, Mint Mobile, T-Mobile USA and Visible. Apple's page does not list Verizon there, but Verizon's own page calls its prepaid eSIM "Ideal for visitors to the U.S."

Travel eSIMs are also sold by companies that are not US networks. Apple describes these as prepaid data plans from a "worldwide service provider", with different data amounts, lengths and countries. Google's Pixel help says the same in one line: a prepaid eSIM from an international carrier avoids roaming charges. We name no seller. Read the seller's own terms, and check that the phone is unlocked first.

What do T-Mobile's US Pass and eSIM by AT&T cost?

T-Mobile's US Pass eSIM cost $25 for 7 days, $30 for 10 days and $35 for 14 days on its prepaid page as read on 30 October 2026, plus taxes and fees.

Every pass includes unlimited talk and text in the US, Mexico and Canada, and unlimited 5G data in the US, of which 50 GB is what T-Mobile calls premium data. Mexico and Canada get 5 GB of fast data. T-Mobile says the pass activates the moment you buy it, so buy it after you land.

T-Mobile's footnote warns that users above 50 GB may be slowed when the network is busy, and that video streams in standard definition.

eSIM by AT&T is sold through AT&T's own app in 1, 7, 15, 30, 90 and 180-day passes, from $3.99 for one day of US data. AT&T's page says data is unlimited for the days bought, with 5 GB of hotspot data before speeds drop to 128 kbps. AT&T may also slow data when the network is busy, and the page does not say whether taxes are added.

AT&T's page adds that it has no network of its own in Canada. Neither T-Mobile's nor AT&T's page, as read, says what identification or payment card a visitor needs.

What does Verizon's visitor eSIM cost, and who can pay for it?

Verizon's visitor eSIM cost $45 to $70 for the first month on its page as read on 30 October 2026. The page carries no date. The page warns that additional taxes and fees may apply. We list the three networks side by side, not as a recommendation.

Verizon's first payment buys a full month of calls, texts and data, not a short pass. The page says there are no credit checks or activation fees. It says nothing about identification.

Three conditions on Verizon's page matter more to a visitor than the price:

• Activation in the US only: the eSIM can be activated only while you are in the U.S., and the My Verizon app checks the phone's location. Before the trip you can download the app, browse the plans and check the phone.
• Payment: Apple Pay, PayPal or a U.S.-based credit or debit card. The page does not say whether a card issued abroad works.
• Two numbers: Verizon suggests keeping your home number for incoming calls and adding a new US number for calls inside the country.

Apple's general advice says a plan can be bought before you travel or after arrival. For Verizon, the carrier's own rule applies: activation waits until you land.

Is roaming on your home plan an option in the USA?

Roaming in the USA is priced by your home provider, not by any US rule. The European Union's Your Europe page says "roam like at home" covers the European Economic Area, Moldova and Ukraine. The United States is not on that list. The EU tells travellers going further to check the cost of roaming with their provider. It adds that many operators choose to extend their offers to other countries.

Apple notes that roaming with an eSIM works the same way as roaming with a physical SIM. Your carrier may also sell a travel pass. Ask before you fly, and compare its price with a month on a US line for the length of your stay.

Where is airport Wi-Fi free in the USA?

Airport Wi-Fi was free at Dallas/Fort Worth, Philadelphia, Chicago O'Hare, LaGuardia and Newark, the five airports whose own pages we could read on 30 October 2026. None of the pages prints a date.

O'Hare's page adds a practical tip: if the login page does not appear, load a web address that does not start with https. Los Angeles, Atlanta and Denver refused our connection, and JFK's page showed no readable text. We make no claim about those four.

Where does the phone signal end in Death Valley, Yellowstone and Denali?

The phone signal ends close to the developed areas in all three parks, and the Park Service says so on each park's pages. Yellowstone tells visitors to check coverage with their provider, and one network can have a signal where another has none. At Great Sand Dunes National Park, Verizon users generally find a signal in the main visitor area, the park says. Users of other carriers may need to be nearer Alamosa.

• Death Valley National Park: the park says there is no cell phone service along most park roads, and help may be many hours away. Its dirt roads have no services and no signal for many miles.
• Yellowstone National Park: masts at Mammoth Hot Springs, West Yellowstone, Old Faithful, Grant Village, Lake Village and Mount Washburn serve most developed areas and the North and West entrances. In summer the number of users can overwhelm the network. The park says texting is usually the most effective way to communicate.
• Denali National Park: the park's pages give the cut-off as about three to four miles along the Park Road from the entrance. Its safety page says three miles, and its goods and services page says Mile 4. The park has no pay phones.
• Gates of the Arctic National Park and Preserve: there is no cell phone service at all. The park recommends two forms of communication in the backcountry, such as a satellite phone and a satellite messenger, many of which have an SOS feature.

Yellowstone's two official figures measure different things. The park's goods and services page, updated on 4 August 2026, says the masts serve most developed areas. A park news release from June 2025 put cellular coverage at about 8% of the park's area. That coverage is intended only for developed areas, not for roads or the backcountry.

Death Valley advises downloading the NPS App before you arrive. Our guides to driving in the USA as a visitor and renting a car in the USA cover the rest of a long drive without coverage.

Where can you get Wi-Fi inside a national park?

Wi-Fi inside a national park is limited to a few buildings, and the Park Service says free Wi-Fi exists only at some visitor centres and facilities. The park pages read on 30 October 2026 name these places:

• Yellowstone: free public Wi-Fi at the Albright Visitor Center, the Old Faithful Visitor Education Center and the West Yellowstone Visitor Information Center. Some hotels and lodges offer it to registered guests.
• Death Valley: very little Wi-Fi, typically at the Furnace Creek Visitor Center and the Stovepipe Wells Ranger Station. The park warns that it frequently goes down or is slow.
• Denali: the Park Service's list of concession facilities with Wi-Fi names the Morino Grill, Riley Creek Mercantile and the Wilderness Access Center. That list does not say whether access is free.

Great Sand Dunes is the counter-example: the park says there is no Wi-Fi in or near the park, because it relies on a limited-capacity phone line.

Does 911 work from a foreign phone without a US plan?

A 911 call from a mobile phone must be passed on by the carrier whatever the caller's subscription. The federal rule, 47 CFR 9.10(b), requires carriers to transmit all wireless 911 calls "without respect to their call validation process". The rule's definition covers a call from a phone using the serving carrier's radio standard. That makes it a rule about subscriptions, not a promise that every foreign handset can attach to every US network.

The call goes to the local emergency answering point. Where none has been designated, it goes to a statewide default answering point instead. Be ready to say where you are: Denali's safety page asks callers to give their location as Denali National Park.

Text to 911 is not available everywhere. The same federal section requires an automatic reply when a text cannot be delivered because the service is unavailable in the area. Call when you can, and text only when you cannot speak.

Phone signal is still needed for any of this. Denali says emergencies in areas without cell service should be reported to a park ranger. Death Valley says to call 911 if you are within service, or to find a ranger. We found no official page confirming that 112 reaches a US operator, so dial 911.

What are the emergency alerts that make a phone sound in the USA?

US emergency alerts are Wireless Emergency Alerts, broadcast by carriers to capable phones in the affected area. The National Weather Service says they are free, need no signup and no app, and do not count towards texting limits. A message arrives with a special tone and vibration, both repeated twice.

The alerts cover extreme weather and flood warnings, local emergencies that need evacuation, AMBER Alerts, Blue Alerts and Presidential Alerts. Newer phones receive messages of up to 360 characters. A Spanish version appears only when the sending authority transmits one. You can opt out of imminent-threat and AMBER alerts, but not Presidential ones.

The Weather Service says visitors receive alerts too, if the phone is capable and the carrier takes part. Its page says nothing about a phone on a foreign SIM. The federal agencies' own alert pages could not be read on 30 October 2026. So treat an alert as a bonus, not a guarantee, and keep an eye on local news and park notices.

How do you dial a US number from your phone?

A US number is dialled from a mobile as +1 followed by ten digits: a three-digit area code and a seven-digit number. The International Telecommunication Union's dialling table gives the United States country code 1, the international prefix 011 for calls leaving the US, and ten-digit national numbers. A park number printed as (907) 683-2276 is +1 907 683 2276 from a foreign phone.

The +1 code is not the USA's alone. The North American Numbering Plan Administrator says the plan includes the US and its territories, Canada and some Caribbean countries. Whether your home provider bills a call to a +1 number in Canada or the Caribbean as international is its own rule.

Toll-free numbers (800, 833, 844, 855, 866, 877 and 888) can fail from abroad. Gates of the Arctic prints its 833 number as "toll-free, USA only". Beside it is the local Alaska number, 907-683-2276, which the park says also works for international callers. Look for the ordinary ten-digit number on any page that lists a toll-free one.

What voltage do US sockets use for a phone charger?

US sockets supply 110-120 V at 60 Hz, according to the Department of Energy. Many other countries use 220-240 V at 50 Hz. Standard 120 V plugs have either two or three prongs: one hot, one neutral and a third for ground.

A charger whose label shows an input range that includes 120 V, such as "INPUT: 110-240V", works in a US socket with only a plug adapter, by Electrical Safety First's guidance. One without that range also needs a voltage converter. Our guide to power plugs and adapters in the USA lists the plug types by country.