New online contract

I was eager to apply online for a new contract due to a special on the S7. To my shock the online sales person made a mistake with the porting of my MTN (prepaid) number to this contract. Vodacom has to collect the phone from my now, -I received yesterday. It is also my responsibility to cancel the contract after three days of collection of this phone from me. I was told I'm unable to cancel the contract now as I still have the phone. I hope that now money will be deducted in the meantime. As a possible new client of Vodacom I'm saddened by this experience and it leaves a sour taste in my mind. Now I have to jump thru hoops for a mistake you made.