Over charge

I have a cellphone contract with Mr Price Mobile, they over changed me, they debited Over R600 and my contact said R119 per Month, I don't even use the sim card as is always offline and network down, when I ask they say is for data, am so disappointed and I don't know where will I get that much money. Worse they said I still need to pay R400 and I wonder how much am I gona pay this month as I don't even use the table anymore. I regret taking the contract and I want to cancel it, i can't afford to pay so much money