I once bought a refurb iPhone 5S when they were still fairly new, it arrived, mint condition, I spent a few hours setting it up and getting everything totally perfect, then I went to apply a glass screen protector and my thumb went straight through the cheap crap screen someone had put on it when I was trying to work out an air bubble around the earpiece...
I had to pay an iCracked repair guy to come and replace the screen for me (I didn't want to touch it) which was pretty reasonable, £60~ I think, and the guy put on a much better quality screen, an expertly applied the glass screen protector for me.
Then I discovered the GPS didn't work, so I sent it back to the company I bought it from for a re-fund... So they got a free screen upgrade courtesy of me, on their jankily refurbed phone they sold me...