******ionate repair cost for well documented IPhone 6 design fault: flickering gray bars and all with glitchy touch functionality

I bought an Iphone 6 Plus (refurbished) from the Sandton IStore 18 months ago for R8000 and was very happy for 18 months. However 2 weeks ago the phone developed a well-documented design fault : " flickering grey bars and all with glitchy touch functionality" https://ifixit.org/blog/8309/iphone-6-plus-gray-flicker-touch-death/ . Thoroughly inconvenient - Ive spent countless hours getting history and banking apps re-established on a temporary phone. I have now been quoted R6 349 for the repair. (I was originally given a R3000 - R4000 estimate by the IStore Sandton sales counter which seemed expensive but acceptable). DISCLOSURE: Per the aforementioned article - the way to fix the glitch is to "twist the phone" and I cracked the screen doing so but this had zero impact on the functionality (factory fault glitch aside) and was understood by the repair agent .