My phone suddenly keeps saying that network is unavailable because I have no SIM card? This has never happened before, and I keep having to turn my phone off and on, and it still won't work. I don't have internet at home, so my phone is the only way that my family can contact me while I'm in university! I'm going back to university this evening, and my phone will not receive or send phone calls. Help? I haven't taken my phone apart, I haven't removed anything, it just stopped connecting this morning. I've turned it off and on a few times when it says that it won't connect, so it'll connect temporarily for a bit, but then I get the memo again.