Locked in forever once you sign up

Been on a Telkom sim-only data contract with Mondo, I received a call to say it was due for an upgrade. I explained that I need voice more than data and was told that it was not possible to change from a data contract to a voice one. After receiving reassurance that I can cancel the renewal within 7 days of requesting it, I agreed to the upgrade. I called the next day to say that I wanted to cancel as I found a package directly from Telkom that suits me better but was told I would only be able to do so after 7 days. I set a reminder and called on the 7th day to cancel and on the 8th to confirm that the cancellation went through. I also sent an email to the customer care email and completed their auto-bot process to request the cancellation. To my sur2, I was charged in April so I called and was given a ***** explanation of there needing to be a 30 day notice despite my explaining that the sales person reassured me that I could cancel immediately in 7 days (which I did). I requested that the cancellation be put through again during that call. I have once again been charged. I called the customer care number on Wednesday and the consultant said that he could not get hold of the cancellation division, he would call me back in an hour. I received no call. Warning, steer clear of this company.