No service on the phone

[Lado]

I am currently in the US and I can not get any network service on my phone. 

[pgn]

USA - Roaming with O2 might help, depending on whether you are on a Contract or PAYG, @Lado 

Try searching for a different network manually, even one that shows as Forbidden (so long as you are not PAYG).

Check your APN if you use an iPhone - it can be set to mobile.o2.co.uk if it is empty.

Contact O2 to check you have no bar on your account - Guide: How to find help & contact O2 has the Social Media links to O2 Support.