Cell C Contract packages.

I took an upgrade with Cell C on October when they had a special... the price for the phone was R999 as per brochure and telephonic sale. Legally the billing for it started in January 2019 yet the previous month December 2018 they billed me for the old contract yet the price was slightly higher than the usual price. In January the contract kicks in and I am to be billed on the 25th but then these guys bill me R1700, when I ask why they tell me I used above my limit and the charge was for extra coverage. The contract sold to me was said to be capped and should I deplete my data and minutes nothing can be done after I also asked for it to be that way.. my last contract was exactly the same. The guy tells me that I used up an excess of data and minutes via a balance allocated to me. I tell them that I do not ever remember signing up for that balance and if possible let them please go bk to telephonic sale and specify my order and me confirming that I want that excess balance. They said they’d open up a case but they never came back to me about it. They have now sent me the February statement with a balance of last months unpaid installment, the balance has come to 3000 for two months. The phone was never R999 as they advertised it seems and whenever I check my balance via *101# it never shows me anything about an excess amount they keep telling me about.