Lack of Communication

I upgraded my contract on the 17th of Feb 2015, the device chosen was a Sony Experia Z3, the phone stopped working exactly 14 days after I received the unit so it was no longer under the 7 day swop out warranty, I took my phone in on the 4th of Mar and explained that the phone turned off although the battery was still over 70% and the unit didn't want to charge. They sent it off and i got the SMS notification of the progress, then on the 13th of Mar saying that I need to pay in excess of R 3 900.00 for the repairs with no explanation, I contacted the store manager and he checked on the system and said that there was no reason and he couldn't understand why it wasn't being covered by the Manufactures warranty, he said he would escalate it and get back to me but that it would take 48 hours, today is the 17th, I have called the store twice with no luck and received another SMS saying that I need to pay over R 3 900.00 to repair the phone and still I have no idea why this is no longer under the manufacturers warranty, my phone has been in repairs now for as long I had the phone myself, I want the phone replaced, not repaired as I assume it will continue giving me issues....14 DAYS hey