Billing ****s- never again!

I entered into a month-to-month contract in 2019 over the phone with one of their agents because I didn't want the commitment of a contract. The contract started at R605 per month, I would pay R650-R670 each month because I wanted to have a month where I wouldn't pay. Of course this didn't happen because I would always get overbilled. They finally changed the contract to R650 so I still paid that amount, but somehow my invoices would still be above that amount. I stopped using their services and filed a cancellation of service request. Nobody contacted me, I was billed R678 on my last bill (no reason why this could be the case since it's uncapped and I always paid before the bill was due). Now they have sent a threatening email demanding over R1500, which makes no sense because I cancelled in February and I paid my January bill. I'm glad I kept my receipts because these people need to be reported to the ombudsmen urgently. I'm not the only one finding their billing process *****. I will never get into a contract with Telkom again!