Credit from data

For 2months i have had no data connection on Mtn through Mondo data sim, MTN was supposed to credit me as per Mondo, I have called both Mtn & Mondo and now i am being told it will be passed, yet they have Debited my Account with another R723 this morning. I am extremely frustrated. Mtn, why do you not contact your customers? Why are you deducting money when you owe me money, Please advise???