Frustrated by Cell C

New contract with cell c. It was confirm to put an limit on, so I phone for limit few days after activation. Within 10 days I couldn't use the internet,the data was finish. Between me and the person that sold this deal on the phone, she said if I don't want the Sim any more no fees will be charge. But according to an sms they sended me I'm liable for an R700 an something an not the R150 as agreed. So I wanted to cancel the contract but they don't want to, because I'm liable for 2months, they say.