Broke my screen replacing my battery.

Smenro Somerset Mall broke my phone screen whilst fixing the battery and then casually informed me the screen has lines on it, do I want to replace the screen? When I took the phone in the screen was perfect but there was an issue with the battery, they could still turn the phone on and check it however they claim that since they never switched it on they cannot say the screen was not like that beforehand. Their mannerism was completely apathetic from the start and they could not care less.