Re-Built iPhone sold at Vodacom as NEW!!

I purchased iPhone 5s 16G at Vodacom The Grove and insured it. This was in April 2015. In June 2015 (2 months later) the phone could not charge anymore. I sent it back to the store for repair and was informed that it was to be sent to vodacom repair centre in Potch, which they did. To my suprise I was informed that there's mismatch between the serial number and IMEI, so the phone could not be repaired. I was advised by the agent at callcentre *** to submit the box which I did but it was still not repaired. The store manager, at the Grove, confirmed the purchase but indicated there was nothing she could do, and advised that I approach HeadOffice. My phone is not working till today. I,m so frustrated.