Using Mobile phone in the USA

[Rob4T]

I`ve given my old phone to my girlfriend in the USA. she`s put a Horizon sim card in it and apparently it does`nt work. Do UK phones only work on networks in the UK. I have used the phone in the US while I was on holiday last year while I was on 02. It connected to AT&T

[Cleoriff · Accepted solution]

@Rob4T 

O2 phones work in the US.  However if it's an old phone, it may be locked to O2.

See if she can get it unlocked whilst there (via an outlet which unlocks phones) and then I would ask her to try a local AT&T sim.

Edited to add unlock advice.

[madasaf1sh]

@Rob4T

Did you mean Verizon?

If so that is one of the networks that might not work, as it may be trying to connect to the CDMA network.

The iPhone for o2 (and in that respect AT&T and T-Mobile) does not support CDMA and will not work Verizon Wireless, the same applies to Android Phones as well.

and to add

"One important thing to note about Verizon Wireless is that many phones are built specifically for the carrier, including its 4G LTE bands. In other words, the common case is that you will not be able to use an AT&T device on Verizon's 4G LTE network."

(edited to add text)