Data charges while at home on WiFi? At Apple Store?

[calvinator]

Apple exchanged my iPhone 5 because of a couple of problems. ON THAT DAY ALONE, my data plan logged 10% of my total monthly data. 2 days later, while at home and on my own WiFi network, Verizon logged another 45% of my entire data billing total in one evening.
WHAT'S WRONG WITH VERIZON'S DATA BILLING?
When and where CAN I TALK TO SOMEONE???
THIS HAS HAPPENED BEFORE - WHAT IS VERIZON DOING WRONG?