Vodacom - not paying back money they owe me!

phoned Vodacom numerous times about money that still gets subtracted from my account even though my contract was cancelled last year in September 2017.

I phoned 23 June (over a month ago) and spoke to a lady. I explained to her that I cancelled my Vodacom data contract in Sept'17 and money is still going off my account. The lady informed me that the cancellation process did not go through properly and that it is a mistake on Vodacom side and that Vodacom will refund me. I asked her to be refunded asap.

On 16 July I phoned again, speaking to a gentleman, explaining the same situation over again, was told again that Vodacom will refund.

On 20 Jul I phoned again seeing that I had no response, explained my story again to another lady and she told me that the account department didn't respond to the query yet (even though this is more than a month later and NO excuse).

I phoned again on the 11th of September and the person who assisted told me that the money will be paid into my account on Friday, 21 September and again no feedback and no money paid back.

I phoned Vodacom again today, 18th September, spoke to 3 x different people and they all told me that they unfortunately can't assist me.

This is the worst service I've ever received. How do I get my money paid back???