Failure to terminate my contract as requested

I first took a cellphone contract with telkom and a few months down the line because i was happy with the contract i took another laptop contract with them. The contract were bundled into one pertaining to payment and that is where the problem begun. My first contract expired and i filled a cancellation form before the expiry date as required but telkom failed to cancell as requested and as a result they c ontinued billing me the same. Unfortunately when i reversed the debit, it also affected the contract (laptop contract) that was still in force. Regardless of my several calls and emails trying to resolve this matter telkom failed to communicate with me and now they handed my account to some debt collecting agency as if i am refusing to pay them. I want to put it on record that i never had a problem paying my account, at some point i owed telkom 3000 on this account and i paid that money. Ijust don't understand why it was so easy for me to get the contract but impossible to terminate. i want telkom to stop being arrogant and take responsibility for their bad service so that we can resolve this matter.