iPhone 4 5.1.1 iOS No service - Error Performing request Unknown Error

Im tired of this !! i have an iPhone 4 firmware 5.1.1 factory unlocked, it works well but sometimes the signal bars going down and super fast go up, then the issue starts, it happens a lot of times at a day, almost all the time, its total bars but its like connectivity freezed because, i cant do anything, not calls, not sending messages and cant request my money info through code because it comes with (Error Performing Request Unknown Error)and cant even contact Telcel with the codes, and that kind of stuff, 0 connectivity with ``100%`` signal!!, i need help, im desesperado, it happens with Cubacel and Telcel, i had a 3GS and that didnt happen with the same SIMS, plz help. I NEED HELP BECAUSE I CAN USE MY A LOT OF DOLLARS PHONE, AND I BUYED FOR THAT, AM VERY DISAPPOINTED, plz reply, Thanks

The WIFI WORKS ALL RIGHT.

We all pay YOU to THIS ``UNKOWN ERRORS``.