Vodacom bad service - struggling to cancel contract

Vodacom has ****ty service. They suspended my service after I cancelled my contract and they continued charge me. Two months later they are informing me that they don't have a record of the call where I requested the cancellation and paid all that was owed etc. Negligence or incompetence or direct ignorance on Vodacom's part. I loaded data beginning of the following month as I expected not to have as per contract. I even advised that the call could have initialised from billing then transferred to cancellations and gave a date when I did the outstanding payment to effect the cancellation but they still couldn't pick it up. Anyhow I am sick and tired of service like this, being held ransom to something I was very clear about. Almost seems like some form of service ********* on vodacom's part someone didn't do their job properly and the customer needs to pay for it.