IThought thiw was an upgradr

so I decided I should upgrade to the new BBZ3. unfortunately the phone went off for no reason and would not turn on. I went into the store where the personnel who was meant to assist me was rude and arrogant. I requested that they cancel my contract which they refused. the phone had no damages (its brand new) but the same problem persisted when checked in store. they then said that they had to do an OBF before I could cancel. They are now refusing to cancel my contract and to give me a new phone. I cannot pay for a problematic brand new cell phone. Really disappointed with Cell C