Being charged for a canceled/paid up cellphone contract

On the 19th of November 2020, I received an SMS from MTN confirming that my 24 months phone contract has come to an end and that I will be on month to month. On the 7th of January 2021 I contacted your contracts department and requested a cancelation of the product and I received confirmation via emails and SMS with ref number *** that it had been cancelled and that I am now on prepaid. January 15th another SMS came through confirming that I am now on prepaid. Funny enough on the 15th my account was debited R1199 I reversed the debit order as I had cancelled the account with you. Now last night I received another SMS stating that I need to make payment at any MTN store for my services to remain active (I don't know which services as now I am on CONTRACT) and that it will affect my credit rating. Once again this month - the 15 of February 2020 another amount of R1514.20 was debited on my account and I have once again reversed this payment. I have emailed your accounts department and was asked to give my info so as they can pick up the account as they can't find it anymore. I find this serviced offered my MTN appalling and disappointing. Please explain and rectify.