T-Mobile inappropriate billing Internet

Once I cancelled my plan to switch to Sprint (T-mobile provided poor customer service in my opinion) my final bill was significant (greater than $500) I arranged with customer service to pay half in December (the month I was billed) and half in January (per Michael, ID #12511336). I mailed the appropriate check.  One week after I mailed the check, T-mobile debited my checking account the full amount owed; which was never authorized.  I called customer service again, was promised a return of the entire amount debited, because the combined amount of the debit and the check I mailed was 1.5 times the amount owed. I called on 12/18, spoke to Lisa (ID #17754340) and the supervisor Charlott (ID#17753964) and was promised a FULL refund (refund # 221843031). A week later, only half of the amount was refunded. I called again and spoke to Leon (#116802950), and again was promised that the remainder would be refunded (Refund #221696108). after my refund was NOT received in the timeframe specified by T-mobile, I called yet again, and spoke to YET another representative (John ID #1744971)who again promised a return of my money (refund # 221975292) As of this complaint I am stilled owed $332.68 by T-Mobile, a month after the original bill date.