over billing

I took a contract with cellc worth R149 per month for 24 months which was ends 15 may 2015. I have been calling customer care line to confirm the last debit they told me but never told me about the extra monthly debits or continuation of the contract. On the last day of the contract they sent airtime worth R153 which we did not agree on then I called customer care asking. They told me to cancel the contract then I did now on the 30th may they debited R153 and R223.99. And also during the cancelation they were convencing me not to cancel rather upgrate. I refused they kept on on telling me to continues as if they are paying for me . Now I don't even have money to pay rent. Like its been happening for long I am even a fraid to keep money in my account anymore. How can u do that? This is theft.