Q: No signal to call or sms  but only i can use internet only in this country

I bay this as a new  iPhone from Dubai, I used in UAE and Oman but when I came to UK iPhone not calling or reserving call, also no signal

I tray all sim cards but not work

I ask some who have experience in iPhone there are say maybe this phone in black list in Uk

So I try to contact carers in UK but with out any   Interest

I wish you can help me

Regard

Qasim