Warning: T-Mobile adding pay per use data without your permission

It turns out that T-Mobile started rolling this out on 15 September to all plans that have smartphones, including family plans where non-smartphones are included. It turns out my daughters' phones were just turned on, but T-Mobile should never allow this to happen without notifying the primary account holder who has authority and control over these phones. I called them up and they said they would block it on these three other non-smartphone lines, but the representative falsely told me it was always part of my plan. I told him I know what is on my plan and that he was wrong.
He said he wasn't going to credit me the $18 for the data used yesterday, but I will call back again and make sure someone credits it back since I did not authorize this change and the charge is ridiculous at $1.99 per MB. With the uncertainty surrounding T-Mobile and crap they pull like this, I am seriously considering leaving them after 9 years. I may give them a couple more months to see how things shake out, but I am not a happy customer at the moment.