IMPOSSIBLE TO CANCEL CONTRACT

I went to MTN branch on 28th Dec to cancel a contract that has run out and is on a month to month basis and was advised retentions dept will call me. This was after trying twice via the phone and getting transferred to retentions who never answer. My contract is still not cancelled, the SMS said contract would be cancelled 29/12/2020. MTN is making it impossible to cancel contracts with them, this is ****************.