RIDICULOUS CHARGE ON MY EPIC CONTRACT

I'm sick and tired of CellC, i am on an EPIC150 Contract and i'm supposed to be paying R189 every month but to my suprise my current bill is R889 and i dont even know how possibly could i have used that much since i stopped using this Sim Card and switched to a prepaid one. For the past 4 months i have paid an average of R1000 and i have tried to cancel this without success. i'm regretting the day i signed up for this rip-off. For this current period i only used up my R100 airtime value and purchased a single 100Mb of Data and i yesterday i had a balance of R2.20 left on my account and about R23 extra usage that i made 2 calls to Mozambique. So tell me how that adds up to R890. My account is always in arrears because of this and i am starting to think that there is a ******* and i want to cancel this because its stressing me every second of my day. Tried calling your 140 and i cant get through since its full of supposedly COMPLAINTS against your bad ripping people service.