UPDATE: Problem solved by switching to AT&T
After 2 Verizon phones, I decided to switch back to AT&T and have not encountered the problem since. AT&T told me that verizon's phone network is older and poorer quality (no shock ATT would say that about a rival), however, I have a new iPhone 5 and I'm experiencing the same call quality I had while I was on my old iPhone 4. Some folks have experienced the same problem on AT&T, but Verizon folks, I encourage you to give AT&T a try to see if it solves your problem. Unfortunately, I dont think the coverage is as good as Verizon, but call quality is my #1 priority with a phone. Good Luck!!!