[Anonymatt]

you say it isn't location dependent, but how about signal?

I notice I have similar issues with a lot of missed calls, but it is usually when I'm in fringe areas. The most annoying part is that my phone will show ~3 bars of signal, and I'll try calling it from a different phone, and it won't go through (On the other phone I'll hear it ring for about 15 seconds). Then as I'm watching my bars they'll drop down to 0, go into roaming (little triangle) and bounce back and forth between 0-3 bars. It is really frustrating, since this is how it is at work, where I spend the majority of my day.