I can recieve and make calls successfully but once connected there is no sound. I can't put the phone on speaker phone either. However, once i plug in some headphones I can hear the caller but they can not hear me. This has happened with my phone several times but the sound usually comes back after about an hour. Today is the first time it hasn't worked all day. I can make texts messages and recieve them. I can make calls and recieve them but I just can't hear anything and neither can they. 'm guessing theres something wrong with the mic. Help?