I just bought a Samsung S3 T-999. The problem is when I switch the cellphone on, it connects to my network but just for a second. The moment that second is gone, I lose signal completely. So it's not like the IMEI is corrupted or something. Moreover, the phone is not asking for an unlock code at all, so I assume it is unlocked too.
What could possibly be the problem? How can I solve it?
This is the screenshot: