Furious about un-asked new contract

I am in the process of cancelling my contract with Telkom in order to get my cellphone number back to prepaid. For some reason they thought I want a new contract on my sim card for data and billed me for it in April 2018!!! I have not used that sim card since February 2018 because I am busy paying off my cancellation fee and they have the audacity to bill me for a data contract I did not ask for on the same number contract I am busy cancelling! Does that make sense! I was told in two separate months the billings department will contact me soon to sort out my issue on my account, however no one calls me. The call center agent rudely said that it is my responsibility to follow up with the billings department as they do not get notifications on the notes they so nicely add to my account. What is the point of adding the note then? I keep on being billed and debit orders are going off on my account but I would just like to know when did I consent verbally and in writing for this new contract that I supposedly asked for? All I wanted was to pay my cancellation fee and do a simswop to a prepaid sim card for my same number. Is that so difficult to understand?