Defective phone sold

I went to renew my contact and purchased and iPhone 6 and 3 months later I returned to the store to return the phone as the screen was lifting. The phone went for a warranty assessment and I was refused a new device or repairs of the device and I was accused of physically damaging the phone, I then asked to speak to the store manager and asked for a copy of my contract, my request was subsequently refused. Could I please have someone from MTN to assist me as I am I long standing customer. I like this matter to be resolved as soon as possible by getting a repaired device/new device or being able to hand in the device to MTN Canal Walk and cancel my contract. I have read up on the Consumer Act of 2011 and if a defective device was sold to the customer and is returned in 6 months a new device should be given to the client or a reimbur*****t.