Hi, I recently bought a Motorola Droid Mini from E-bay. It is unlocked, and I have a Simple Mobile sim and plan. The problem is the sial keeps going up and down and even when it is in 3 bars I can't text nor call. The thing says" Simple Mobile 4G". The 4G works fine, but I just can't seem to call or text people. Sometimes I can, but then it just disconnects. I don't know if the problem is the phone, the sim, or the carrier. Anyone have any option?