Cancellation nightmare continues

Just as I thought that this whole nightmare has finally come to an end it starts all over again. After my last review Vodacom has done what they promised and credited the amount that were incorrectly charged and finally cancelled my account. Or so I thought, but to my astonishment I have just received invoices for July and August..... I have sent emails and private responses to the previous review but no joy. I honestly do not know what else to do. Is it really that difficult to cancel a contract??