Being charged more than the contract deal agreed on

Telkom is messing with me, I'm on a broadband WIFI package for R449, and for the past 2 months telkom is charging me R557 coz they say now they're charging me a separate R150 for the device (which was never explained to me when sold the package). The lady by the name of Refilwe from the sales department confirmed that for last month it was a once of charge to offset the cost of device but from this month I will be paying R449 as originally agreed. My shook is that I now spoke to David who just wanted to explain the bill and not actually get to the point of the matter that I'm being charged extra for something that wasn't explained on the sale call. He even hung up. I also asked him to listen to the sale call but I was just ignored. I hate Telkom with all there is in live, the worst service provider on the planet. I wish it could lose more clients.