I have recently moved from T-Mobile to Verizon. And Activated my Service in my Friends account, which I received my sim on Dec13th, but Verizon charged me from Dec 6th to Dec 16th.
The plan gets charged for the 16th of every month. But when I was about to pay the bill, I saw an additional monthly charge of 50$.
Can you please provide more information about the detailed charges on your first bill? Did you initiate the switch to Verizon Wireless on Dec 6th? The charge between Dec 6 and the 16th might be partial month service charge. There should also be a activation fee for the line added. Since you joined another person's account, you need to clarify which charges are his portion and which are yours.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.