Pathetic service from Telkom as warned by others

I have cancelled my ADSL landline with Telkom on 18 March 2020. My ISP is with MWEB. Now I am told 10 days before the cancellation should be effective, that I should cancellation again, because I did not cancel the landline. This means that I need to pay another months for this really pathetic service. To date I have not received a call from Telkom (as promised with the previous cancellation). I intend to block the debit order after the 1st May 2020, and I WILL NOT pay any additional subscription fees.