Debt collection on a service cancelled more than a year ago

Telkom's different debt collectors keep calling although I have canceled my service with them more than a year ago. I did my cancellation and as per the norm with their 30 day delay I would gladly pay. But not the R900+ and R1100+ the different debt collectors are Demanding.... Sort out your system and I will pay the month owed + the month delay on my cancelled landline