Starting from yesterday afternoon I couldn't receive or send any text messages. Same with calling people. This morning I tried sending a text message in class and it worked, but once I left the classroom and started walking back to my dorm the same problem happens again. Also, my roommate also has at&t, but this problem did not happen to her. I have a Sony Ericson C905a. im in San Jose, California. Can somebody please help me with this problem? It is very frustrating and annoying.