Won't respond to emails IPhone 6 Plus needs repair

In September 2015 my IPhone 6 Plus still under warranty was not turning on it was sent to Vodacom Durban repair center where they could not fix it it was then sent to JHB where after about 6 weeks and a lot of begging that the unit please be replaced due to the fact they can not fix it the unit was sent back they replaced the battery. The unit was never used and I waited till I had wifi to restore the unit when I tried the unit once again was dead and sent for repairs again now The repairs department says I need to pay R4500 odd and then they will replace the unit as the motherboard is broken I can not see if something was fixed properly how it can break lying in a draw. I have sent numerous email to repairs escalations I recieved one reply that they cant find the IMEI I then sent them the job number. The phone has now been with them for weeks and I have waited since Monday for a reply from Vodacom repairs and still not heard anything but the reply mail clearly states all queries will be dealt with in 24 hours. I gave Vodacom a opportunity to repair the unit and according to the CPA if you can't repair the next recourse is to replace. I feel it only fair they reply and replace.