Cell on repairs for 4 months no response

I bought the phone from this store year back and the phone is under Furn rite insure whom is contracted to the store. I have been sending the phone on repairs in and out. Last time the phone stayed for a full year i have been checking till i got the phone. Last year November i took in the phone again and the cashier this time was Julian and the store manager is Sharon. Julian took my phone for repairs and when he took the phone i ask him if he will need my card to check on system he said not the phone will take 2 to 3 weeks. I waited and waited till the day he told me the phone can not be fixed but i must pay R350 which is required by MTN i said but my insurer never wanted money before why now. He realize he took the phone to the wrong service provider but he is refusing to pay the money. Sharon the manager has not been helpful she just ignore me when ever i go to the store. on the ***6 i call Sharon said Julian will pay for the phone because he took it to the wrong place when i spoke to Julian to confirm he said he will never pay out of his money i can take the case further if i want to. Sharon also said i can go to the police if i want to she was rude and shouting me :(