AutoPay Scam

I was reviewing my T-Mobile AutoPay bill and found that T-Mobile has been billing me twice a month for the past year and 3 times in April!!! I call T-Mobile numerous time and customer service is telling me that T-Mobile is only billing me once a month.  But my bank statement is telling me different, so I had my bank call T-Mobile and they were able to get the last 2 month credit for double charging me. Here my issue why credit 2 months when this problem has been going on for a year! Please check your bill to see if this can be happening to you.  SOMEONE IS TAKING MONEY OUT OF MY CHECKING ACCOUNT THOUGH AUTOPAY!