Mtn
Contract not cancelled

My two year contract ended 25th July. I called in to cancel a few months prior and was given the option of rather converting it to prepaid. I called in on the 25th July and was told it was done. Now I have received an invoice because the contract is not cancelled. Please rectify this immediately. I will not pay for a contract that should be cancelled. Check my call records and you will see how many times I called in to make sure it will be cancelled on time.