iPhone screen coming off

Ive had my iPhone 6 (brand new) since I got it replaced two months ago.

I still have a couple of months left of warranty (until October)

I have recently noticed the screen has started coming loose, where there is a little gap between the screen and the case , so that if you look at the phone sideways where the home button, headphones port is located on you can see that its not attached. Will it entirely come off?

When i got my phone replaced I paid for it, so its supposed to be brand new, I haven't taken off the case I bought that day, maybe here and there only to clean the phone with a dry cloth.. thats when I noticed that it wasn't fully attached. Will apply fix or replace it?

Please Help! I made an appointment for this coming thursday, I hope i don't have to pay more money than I already did..