Vodacom is a ****

Last year April I took a phone contract with Vodacom, it included data and minutes. This year in Feb I get called by one of their agents, asked me if I'd like to swap my data and minutes with airtime and NO ADDITIONAL COST. I agreed and lo and behold, I was billed almost double for that migration. I called customer support and asked to speak to their supervisor, who promised me it'll be reversed and apologized that I was deceived. A few months later I'm still calling vodacom to get this resolved because every person I speak to, advises me that it's fixed but come end of the month, my account is overcharged. I have tried everything and clearly you can't win dealing with *****sters.