Picture mail usage?

[erockvr6]

Quick question, I just got my bill and I got charged the maximum amount for data usage, which is $75.00, as I do not have unlimited data- I know I should add it but I figured with wifi at work and home I wouldnt need it- I do however have unlimited text, pics, and vids, so my question is whether or not when I connect to Sprint Picture mail it is using data. The CS rep told me when I got the phone that as long as I had unlimited pics it would not charge me. If thats the case than what is using data? If I go on the internet Wi-Fi is enabled, and if I update the weather Wi-Fi is enabled. Is it possible that these are using data instead of Wi-Fi? The other CS rep told me to take the phone to a Sprint store for a diagnostic check to see why the data is being used, is this possible? I searched but couldnt find any relevent topics, also disabling data is not an option as I need pic mail.