False Offer

I am very disappointed, I sign up for 6 mth mtnchoice 20GB X469. After 6 months when I tried to cancel I dial 135 and was advise that my contract is 24mths, I went to the store with my contract and their send and E-ticket, I called 135 after 3 days as advise by store consultant, till today my contract is not cancelled they send me from post to pillar, now I am sitting with the contract that I can't afford, they advise me to pay cancellation fee and I can't be liable for the store consultant negligence/error . When I go to the store every time they are offline. I sent email to the head office till today no response.