They will not cancel my data contract!

I have been trying to cancel my data contract since December and they have not since cancelled it. I called in December and then got charged (incl. January) and since called again this month and I have not received a cancellation notification but received and invoice and statement! I do not recommend using Vodacom as this is the second contract that I have tried to cancel and they do not cancel!!!! Please, it is not my fault if your debit order bounces!!!!

I am also unable to get a reference number as when I ask they inform that it will be sms'd but it never comes!