MTN forced a month to month contract without consent

I called MTN on the 20th June to cancel a contract was expiring in the same month,was told I'll be billed for the 30days since I didn't give a month's notice which I was fine with. I was sent documents to migrate the nr to a prepaid service which I filled in the same day and sent through to MTN as per provided e-mail. I was sent yhe bill due for July which I paid in full thinking I was done with the contract. August a bill of R95 was sent which I paid thinking it was the shortfall which I was not aware of ,then now this month again another bill of R95 which I refuse to pay ad it seems MTN decided to force me on a month on month contract which I didn't sign nor agree to. They really need to sort their mess out,we are all struggling as it is for them to do such underhand tactics,I'm disgusted and very angry about this since I've been a loyal customer of over 20 years with 2 active contracts but this is the service and thank you for my loyalty I get. They can really do better than thiis