Unable to cancel Telkom - bill just keeps running

Due to financial constraints, I called Telkom a few months ago and requested to cancel my month-to-month LTE SIM until I am ready to pay again. However they said they were unable to cancel my service unless my account is fully paid. However, I did not have the money to pay. So every month they kept billing me without providing ANY SERVICE at all. Now that I received my December bonus, I logged into the Telkom website to pay the bill and see it is now R3583 already!!! So I have to pay for something I never received? This just does not feel right to me. Why is it not possible to cancel a month-to-month agreement? Now I will cancel FOR SURE!! I absolutely do not mind if I have to pay for a service which I did receive, or if there was a contract in place to force me to pay, but being bul**** into paying just because you are a bully does not sit well with me at all.