Samsung S7 Edge flickering screen...

I am absolutely livid with Canal Walk service centre. On Friday afternoon I took my Samsung S7 out of my pocket and discovered the screen was unreadable as the entire screen except for the very top portion was flickering. On Saturday sometime during the day the screen was normal for about 1 minute and then started flickering again. I took the handset to Canal Walk service centre today and they refused outright to fix my phone under warranty as the ADH warranty has expired (handset will be 24 months old in November 2018). The phone has never fallen and has been in a leather folio pouch since the day I received it. They claim it has physical damage due to a tiny mark on the corner of the phone. Who knows how it got there or if they themselves put it there. Nevertheless I am highly highly offended by this . To me this smacks of arrogance and acting in bad faith. I only have Samsung handsets in my household due to the 2 year warranty and the last and only other time I had an issue with my handset (Note 4) it was sorted out promptly at the Waterfront service centre. This Note 4 by the way still looks brand new after 3 and a half years service as it is in the same type of pouch. I have a had an S2, S3 mini, Ace, Note2, Note4 and now the S7 Edge. If Samsung does not fix my S7 Edge under warranty as it is a GENUINE claim I will most certainly never buy a Samsung product ever again. There is nothing more abhorrent to me than someone who does not honour their warranties. I switched from LG to Samsung for this reason and Budget Insurance to Santam for that very reason so this is not threat it is what I do when I get horrible service. Please sort out this mess ASAP as I have been without my handset since Friday and I cannot work properly. I cannot access email, whatsapp, my contacts, my vpn token etc.. Logic dictates that if was physical damage the screen would not have worked normally on Saturday. It was if they were searching high and low for something to refuse my warranty claim. They even took my screen protector off and when they found no cracks or scratches they looked for a pinhole. I cannot even just get another brand of phone as my backup can only be restored to the S7. My backup is 8GB in size so yes I have a lot to lose.