Display IC power issues!

Hello everyone.. thanks for taking time to read my question..

I passed on my 6S to my wife after I moved to a 7 Plus.. the iPhone 6S was working perfectly.. has been dropped a few times but nothing to damage it.. two months post warranty the phone just went blank.. the screen displayed two vertical lines ( can’t recollect what colour my wife mentioned) she tried a reset holding the power and home button.. phone screen was blank.. she pressed the home button and got a response but still no display.. unfortunately she doesn’t have the habit of backing up or syncing with iTunes so connecting to a PC said she had to enter the passcode.. but no response or display from the screen..

I passed it to a friend that is a pretty good with electronics.. he checked it said the display was at fault got it replaced and gave it to me.. ten minutes later I was updating to iOS 11.0.1 and the phone restarted and the display went blank again.. same status as above.. called my friend and he checked it again.. got another display.. fixed it and blew again.. he said it’s probably something with the display IC and checked that.. said it was allowing more power than was required.. after some micro soldering he got that fixed but busted another display..

I have never come across this with others using a 6S.. couldn’t find anything on the Internet.. is it wise to try fixing this, is there a way to fix it or should I just dump it and get her another iPhone..

I’m from India and iPhones retail 40% more than the price in the US..

Thanks for your feedback..