Vodacom ripping me off - data and appalling servic

Since my Vodacom 5GB data bundle contract was renewed last year, the data would run out after 2 weeks. I suspect there was a mistake when they renewed the contract and gave me less data than I was paying for. Because of the insane fees for premature contract cancellation, in January I asked to migrate to 500MB until I can cancel the contract. This was not done, and I resolved the matter on 1 February. They debited R280 for the 5GB bundle at the beginning of March rather than the R60 for 500MB. They now insist that it is because the migration was only processed on 1 Feb. This, of course, was an error on their part, which they expect me to pay for. I'm absolutely appalled by their service. I take this seriously, as it is theft plain and simple. They only look at their \system"and do not acknowledge human error on their part and take necessary steps to correct it for the sake of their customers. Absolutely livid and appalled."""