I have an original iPhone (8GB) with jailbroken and unlocked OS 3.1.3 and T-Mobile in the U.S. In the last couple of months a lot of strange things have been happening. I get calls but the phone doesn't ring - I only know abut them because of the missed call notice when I use the iPhone. I also get the sound of a voice message, but when I check them there is no voice message. Has anyone else experienced such problems?

Thanks!