Backup assistant does not accrue MB charges...
When you blocked applications from being downloaded, this does not block those that are already available from being used.
The BIG CULPRIT is VZTones deluxe. (the kids... they love the ringtones) Get your hands on the phone, search the media center/ get-it-now menu for any application, and Remove it. The other possible culprit is the canceling of subscription content from the Media Center... this can also incur MB data charges. This does not apply to outright purchases, only the monthly-billed stuff
most applications downloaded often check for updates, etc., thus they access the web, thus, the incurr a download. this happens ever once in awhile for me (I downloaded scrabble).
On your bill, Premium SMS services will also show as "downloads." Does it have a "short-code" beside it?
If it does; you can plug the code into Google and usually figure out what it is, otherwise VZW customer service CAN use that code to identify where the charge is coming from.
You don't have to believe me...
Backup assistant DOES incur MB charges for the initial download. The daily updates (sync) do NOT.
Simply having the application on your phone bills you nothing, after the initial download. (assuming you are registered for MyVerizon, so that you don't have to pay the $1.99/month for the service itself)