Have you reviewed the on board data counter on your phone to compare to the bill data usage and see which applications are using the data?
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
We are sorry to hear your data was used up. We know how important it is to see what has changed in your usage, and we will be glad to help you see what is going on. To confirm, have you made any recent changes with your device? Also, how frequently do you use your phone? DavidR_VZW