You are not being billed extra. In order to move your due date, your bill cycle is changed. Since you said 2 weeks, you would get one wonky bill for a full month plus 2 weeks. Your next bill, with your NEW BILL CYCLE will be due on the NEW DUE DATE, which will be 23 days after your bill closes.
Didnt Verizon explain you would have a different bill cycle and a prorated bill?
Example: if your bill is usually $600, and you moved it by 15 days, you would have either a $900 bill for one month, or an interrum bill of $300, then your regular bill of $600 2 weeks later.
Either way you’re paying for the same number of days service.