Watch Out! Apple Authorised Resellers/Repair Centres might not be, and then you're in trouble with repairs

In July 2014 I got a beautiful new iPhone 5 through my cell phone contract. A month later, for the first time in my life, I dropped the phone and broke the screen. Unfortunately I also damaged the digitizer. Not long after this, I sent the phone in to C3, a company in Caroline Crescent that I knew to be an Apple Authorised supplier and repairer. They repaired the phone and sent it back. As I was restoring my data onto my phone, the electricity went off and the phone got *******ed. I could not afford to send the phone for repair again at that time, so I kept it in its box for the next 15 or so months. The battery of the phone I had to go back to, an iPhone 4, is starting to show its age and I decided to get the iPhone 5 restored to factory settings via the Apple iStore in Cresta. My son took it in, asked specifically for a quote, and we heard nothing more for a week or so. Then I received an SMS saying it was going in to Diagnostics. A day or so later I got another SMS saying it was on its way back to the Cresta iStore, followed by one saying I should go and collect it soonest. This morning I went in to collect the phone, a little concerned that they hadn't quoted me, but confident that it was fixed as I didn't think the problem was especially big -- maybe reinstall software or something. NOT SO. I got there to find out that the screen and digitiser that C3, the supposedly Apple Authorised repair centre, had installed third party parts, and Apple now refuses to even look at it. After some 20+ years of business, during which I bought both software and hardware from them, C3 has disappeared and seems to have closed down. Having thought I was doing the right thing by going to a specifically Apple Authorised organisation, I find I am stuck with a very expensive drinks coaster. I got perhaps a month's use from an object I am still paying off. I feel extremely ill-used. Surely Apple has a responsibility to ensure that the organisations it authorises actually behave properly and don't set long-term, loyal Apple customers up for disaster? I have been using Apple since before the Macintosh was launched in 1984, and when they brought phones out, there was no question what phone I would get on my next upgrade. There is now a big question. My son has a Huawei which is behaving very nicely, and my husband has a Samsung that has also proved excellent. My next upgrade is in July. With tears running down my face, I think I'm going to have to step away from Apple.