PHONE WAS NOT CHARGING

I sent my phone to mtn store in midrand on 23/01/2015 to send it to mtn repair centre,I sent it with my proof of delivery because they didn't fix the problem in november 2014 because when they delivery the phone they didn't leave so I had to phone mtn direct and request that proof of delivery.I bought the phone towards the end of may 2014. three weeks after I sent the phone I received smses saying the phone has been assessed and the qoute is R449.83 ,I have accepted that qoute .a week after I have accepted the qoute ,i received same smses saying same thing then I called mtn repair centre asking when am i going to get my phone they told me that ,they sent it to sony striaght ,I asked them what they were assessing ,they told me its a mistake.they told me the problem with my phone is the USB its broken.the reason of accepting the qoute is I was told the warranty does not cover that part(broken usb).now its been a month and two weeks waiting for them to fix my phone and I am paying every month because its a contract phone.