I'm having this problem with my iPhone. It started sometime yesterday. I have 2-4 bars of reception at all times. I can only make calls to certain contacts at certain times, it's sort of hard to explain. When I make a call sometimes there will be no dial tone, and after 10-15 seconds it says call failed. When people call me, my iPhone doesn't ring. Sometimes when it does ring, says call failed right when I pick it up. Other times it works, again very weird... Never had this problem with any phone I've owned. Any ideas on what's going on? I'm on the Verizon network, and this is my 2nd replacement iPhone.