Contract cancelled during expiry month and still handed over to collection service

I had a contract with Vodacom that expired in December of 2016. Due to the fact that I wanted them to convert the contract to pre-paid. I phoned them during December and asked them to cancel the contract and \I was given a cancellation reference number.

In March of 2017 I received a call from Vodacom that I owned Vodacom money and that I would be handed over if this was not paid. Again i told them that I had cancelled my contract and the operator told me not to worry and gave me another cancellation number.

Its now September and since then I have received numerous calls from MBD Collection Services on behalf of Vodacom querying the same account that was cancelled months ago. No matter how many times I email info through to this firm , nothing seems to come of it and the next month I receive another phone call.

At the end of the day due to a mistake made by Vodacom I could be blacklisted.

Vodacom you truly are the most unprofessional company I have ever had the misfortune to deal with. Your service is beyond pathetic.

Regards Allen