Faulty screenprotector or fitting thereof.

I visited IFix in Brooklyn on 27/02/2018 for a return button repair on my iphone. They did not have stock and ordered parts. No prblem with that even though they inform me regularly that they are still awaiting parts. I subsequently bought a new cover and screen protector which was fitted by the rep in store. I flew to Cape Town the next day and then saw that the screen started to crack spontaneously at the corners-no fall or damage from my part. Currently the phone looks ********** and I will have to replace it. I was in Cape Town for a week and visited the store yesterday where I was informed that the screen protectors are not guaranteed and they are not prepared to replace the screen protector. The fact that it probably a faulty screen or that the rep did not fit it properly was wavered by the store manager. I feel that I am entitled to courteous service and considerateness in this regard and want Ifix to replace my screen protector