Mislead extra fees

I opened an account with sunglass hut in September 2015 the guy told me I will get a 10% for my first purchase and that my installment will be R150 I will only be charged interest when I don't pay on time which makes sense.So my balance was R1 640 so for 4 months I have been paying R200 and I haven't been receiving any statement untill I decided to go sunglass hut by the Glen asked the to call Rcs to my suprise and shock I was told that my remaining balance is<br> R1 374,85 and that every month I am charged for service fees,interest and insurance and that my installment will never be the same as it depends on my outstanding balance.I was mislead by the sales guy and my consumer right were Vialated if I knew any better I was going to do a cash purchase.