Wont ring, receive and text but 3G

Hey guys

First thing I need to say that my iphone is legal, just unlocked it at a carrier store.

My phone shows even full signal strength and I can browser with 3G. But it has a problem that it wont ring, receive. SMS function is the same, cant send and receive either. When I try ringing to someone, it shows "call end" after 1s .

Tried to restore as a new phone, do *#31#, inactive 3G but nothing work =(.

Any solution or which part should i replace?

Will pay you 10$ if you can find me a solution that I wont have to sell it.

REgards

Ekiong