Complaint to MTN

I had two contracts with MTN and cancelled both in July. Cancellation fee was paid to both contracts.There was no debit order in August meaning the contracts were cancelled. On the 01-11-2025, MTN debited certain amount and I disputed the transaction. I’m receiving message stating I must pay or else my credit rating will be affected. I’m so disappointed cause I contacted MTN and the consultants were transferring me to different departments and I still did not get help. Last option is Ombudsman.