Booked in a perfect phone, recieved it back broken !!!!!

So i had a minor issue with my phone that i wanted to get fixed, it is something called a Ghost touch, what this is, the phone basically operates by itself from time to time, opens and closes apps, scrolls through your thing etc. So i booked it in for repair at istore Brooklyn and it was sent to the repairs center. I get there yesterday to collect my device, The phone looks physically fine no scratches or marks that i did not cause, but the phone is flat. I asked the consultant to check the trade in value of the phone as my upgrade date is this year and she then takes the phone and puts it on charge. She then asked me everything she needs to know about the device and handed the device back to me, at this stage the device was still switched off. So i stand there and turned it on, and i saw that the display if all Green and not working. So i asked her what happend to my phone as i did not hand it in like this, and all she said to me was she cant say and she cant help, i must replace the screen.

So my issue is, i booked in a perfectly good phone with an software issue and got the same phone back with a broken display and now I HAVE TO PAY TO FIX IT.

THIS SHOULD BE FIXED WITHOUT CHARGE AS I DID NOT HAND THE PHONE IN LIKE THAT. I hope this is not how apple makes money off of people. I am a first time apple user and have been using my apple for about a year and a half now. and now i wonder if i should go back to android as i never had this with them.

How do we get this fixed.????