Green screen on my iphone 6s

Please help, i took my iPhone 6s to get a replacement battery , but when they took the back off Apple damaged my phone, they gave me a replacement , which in March the screen went black and it died , about 3 weeks later i decided to take a look at it and put the charger in and it just came on. This morning the screen had gone green and I can’t do anything with it, any ideas. Or do i get in touch with Apple store