This week I updated my 3GS to iOS4, and ever since my iPhone is barely working, even though it shows a full 5 bars of reception. - The 5 bars are thanks to the AT&T micro cell, which sits literally 10 feet away from my home-office desk. When people call me, they get a busy signal (it doesn't even go to voice mail). When I try to make a call, it says "call failed" in nearly every attempt. The other two iPhones in my house are still working (albeit not without issue) running iOS3.x I've always believed (and still want to) that the reception issue was the laughable AT&T network, but now I am not so sure... Could there be something new in iOS4 (software switching signal management - forgive me as I know very little about this sort of thing) that is making this an issue? My iPhone is now essentially useless as a phone in and around my house.