charging me for a contract that came to an end in March 2022. please retract it

Hi I have been querying my account since December 2021, Can someone please reply to me. I have been charged with an overpayment for a month when my contract came to an end. I have instructed MTN to cancel the contract before and in the month it was coming to an end. I have called in, sent a number of emails to the CEO and to MTN to get this resolved and to this date I see my account has still not been resolved and this amount is still reflecting in my account. Can someone please sort this out as this is frustrating to have to ask MTN to treatract the amount you keep invoicing me on. I still have 1 contract and my contract has always been up to date. Please sort this out as it's a bad reflection on my name AND I THINK THIS IS UNFAIR. I have been getting calls from MTN and email saying this will be resolved just to find out it's a **** email. People wanting my bank details wanting me to share OTP numbers so my problem does not get resolved. This has been going on since March 2022. I keep writing emails and having to call in by no one assists me. Regards Sharlene Naidoo