I have a Sony M4 Aqua which seems to be riddled with bugs. When it is working it is great but I just I lurch from one problem to another with this phone. Currently I cannot get it to ring. It vibrates on an incoming call but it does not play the selected ringtone. I have tried turning it on and off and changing the ringtone to no avail.
I'm really sorry that you're having issues with your phone. I want to get this all sorted for you. Is the phone on Silent mode by any chance? This would indicate why it's only vibrating. To disable this, hold the volume up key. Let me know as soon as you can.