Solution towards this matter

I bought a contract iPhone @vodacom store which was not in my budget but my sales rep convinced me and never explained the expectations so now I tried to return the phone they refused to take it back, my cancellation fee will cost +/- R12000 they say of which I don't understand because the phone is not used and it's the fourth day with this phone, the 7days period is not yet finished...I'd really appreciate your help