MTN - incorrectly debited my account even with a cancelled contract

I contacted the call centre to cancell my contract in Nov 2021. My bank account was still debited on 31/12/2021 for triple the inital contract amount. I contacted the MTN call centre numerous times to follow up and been pushed from pillar to post with no reply and been pushed from the contracts deptments to billing. I even sent their complaints department a few emails, received read receipts however still no feedback.