MTN double debits my account for no reason

My debit order went off yesterday. And found that MTN deducted double for my contract. When I called I was told that I was overdue for a payment for March 2020. I'm sorry but why was my contract upgraded then in October 2020 and was does my statement not show its overdue. I sent proof of payments via debit order yesterday to *** and I have not received feedback. I want my money back as I have had my contracts with MTN for over 10 years and never defaulted. Is this how they treat customers. It's pathetic. I need action taken against them for deducting over R1400 extra for payments I do not owe or know about. No one called me to even advise my I'm over due.