Vodacom overcharging on Red contract deal

I am having trouble with my Vodacom Red package since I migrated to a business plan. It's going on 5 months that I am being overcharged in access of R1000 a month by Vodacom, everytime I enquire they tell me that they are working on the problem and will give me credit. I am fed up with Vodacom, empty promises and terrible customer service, and this on a business contract.