Telkom refuses to cancel contract even when it ended and I paid for services i did not use.

I cancelled a sim-only contract with Telkom due to poor network. The continued to charge me, I stopped paying they blocked my services but still continued charging me. When the contract was supposed to end they transferred my contract to month-to-month contract without my consent and continued charging me. Eventually I asked them to cancel the contract again and promised to pay all the billing, I did but contract is still not cancelled and I am still being charged.