Trying to change my data plan for 5 months

Took out a contract with Cell C in July sometimes. Sales consultant sold a package to me for 1 gig data and 25 free min for R149 a month, since the first month I've been paying between R850 - R450. Every month I'm phoning in to the customer care and everytime they promised me that they have changed it. My tablet went in for repairs and for a month I haven't used it, but this month payment is R308 and I haven't even used my data or my free minutes, but I have to pay for who knows what. Now my services is suspended for no payment. Phoning customer care and the guy is so rude he refuses to give me my reference number, maybe he is scared that I'll report him for the poor service he gave and when I asked for the reference number again, he put the phone down! What the hell is going on? Maybe I must take this further as it is false advertising from Cell C side? Customer service sucks