Roaming my MTN line in USA

Can't make calls on my MTN and also can't receive calls have try many things still not working and also MTN network not connecting why all most three weeks am in USA...

My MTN line stop displaying network bars on the phone, I no longer receive calls nor SMS on my line.

Ever since I entered UK in Oct 4, there's no MTN signal in my phone, I lived in uk and line has been roamed and about 4000 naira was paid to let my line to stay active yet i...