wrong info regarding contract

I app**** for an upgrade from cell c in heidelberg. The sales consultant made a mistake and admitted to it. I wanted a SmartData 3GB cintract which would include the Samsung tablet. She informed me that i would pay an amount of R186 till end Feb which is prorata because i did an early upgrade. The original amount for this contract is R339. I went to cell c mall @reds in centurion to enquire about data that i am paying for but dont receive. After analysing the account and contract they discovered that i was on a smartChat 3GB which is not what i wanted. After a few calls with heidelberg they told me i would receive 3gb data anytime AND 3gb nit3 data and what im getting now is prorata... i am frustrated and furious as they mislead customers and make up their own package and mislead clients. I am now at that stage where i want to end the contract with them and they will be held responsible for the loss!!! Oh and not to forget that my line has been disconnected once already as the sales consultant told me to pay R186. Which i did. Only to receive a phone call a few days later that my account is outstanding by R331