I bought this unlocked Samsung Galaxy Note II about 9 months ago, and it worked perfectly. All of sudden, it stopped recognizing the network. It keeps saying that it's unable to connect, but it can recognize T-mobile signals. It looks like the phone knows that there is a signal but is unable to connect to the network. Everything on this phone has worked very well other than this network problem. I can use WiFi perfectly, but I cannot make or receive calls. Would you please help me? Thank you so much.