I have the same issue.. Had the phone replaced at a Verizon store. New SIM chip.. worked for about 12 hrs.. now it's back to dropping calls about 30-45 seconds in.. VERY frustrating..
It was something about the programming on Verizon side. It took two trips to the Verizon store, and they had to call and work with tech support. It took about 45 minutes and it was resolved.