Mine is doing the same. I can be right next to it and all of a sudden there is a voice message from a missed call. No ring sounds or vibration what so ever. I don't see a solution to this on this forum yet or have i missed it?
Re: Galaxy s2 cannot download updates or new apps
Sounds like the #9900# is the answer but I tried this but my phone is coming up "Connection problem or Invalid MMI code" any ideas?