Complaint about MTN contact

Hi there I got my phone contract in June 2020, after a while I saw my rooter that I got 3 months after my cellphone contract that it was off.. They told me I have an outstanding amount of R425, but I paid my account fully every month.. I was there so many times but nobody is coming back to MTN, they even sented my bank statements in... I called head office and they keep on telling me I have an outstanding amount... They told me I didn't pay July, but the debit order didn't go through because I forgot to transfer the money at that moment but a few days later I did go pay it with my card by MTN store self... They deducted R 812 the 2 September twice, and they weren't supposed to..MTN told me I must reverse it and then come and pay the right amount.. So I did what they told me to do... Now suddenly I have an outstanding amount. I was there so many times,And they can't find the problem,They tried to deduct the 2 October the R740 and the outstanding amount together... After I already paid my account of R 740 of my two contracts together... I have the bank statements on my phone if you want to see them.. Then you can see for yourself that I paid every month.. There were times that the debit orders didn't go off or they deducted it twice then I paid the right amount later... But I did pay every month, so hope you can help me please.. Greetings.. Thanks