Default [Q] GS3 with problem in signal

Hello people. The time was using a SIM chip in my S3 but it only worked the data network and no phone calls. It displays the H + icon and access the internet without problems, but does not do phone calls, appear Mobile network not available.
So I changed my carrier and everything started to work until yesterday the same problem happened again. The IMEI number is correct.

Could someone help me? Grateful.