Contract cancelled 4 - but still getting invoiced

My 24 month contract came to an end in December and I cancelled the contract via the call centre as well as with a mail to Telkom Cancellations department using the requested template. In January I got the bill and paid thinking its probably just the one month notice. I however sent the cancellation mail again after talking to the contact centre. This time i got a response from the contract centre, stating that they received my mail and will call me within 48 HRS to close. Nothing happened and in March the debit order went off again.I phoned Telkom again and told them that I had now cancelled my debit order and they said not to worry they will make sure that the order is cancelled this time. Surprise, surprise I got my invoice again today for April. The March debit order did not go off due to the block but is now marked as overdue. As my service was cancelled 4 months ago via the Telkom process I will.