MTN harassment to pay invoice after failing to cancel expired contract I requested them to cancel.

My name is Pule Molahlehi and my MTN data contract BA*** expired in Nov 2021 and I was billed month to month in Dec, in January I was billed R999 and I went to Table Bay Mall to enquire and the consultant could not figure out what it was for. He said he had enquired with the head office and will revert back but never did. I reversed the amount and the service was terminated. I subsequently called the call centre to cancel the contract but could not get assistance because the consultant said the system is offline. I sent an email to the call centre for cancellation and the retention department responded and I requested the cancellation of the contract. This was never done, I sent follow up emails to the retention department but my request was never actioned and I kept on receiving invoices. I subsequently went to the Table Bay Mall branch to complete the forms. Only in April the request was actioned. I made several calls to the call centre to request the correction of the mistake. I was promised that the billing department was requested to cancel the invoice and make it zero. This has never happened and I have an outstanding amount on my name. Retention department failed to do their work, I must now pay even for the data I never received