Upgrading to an iphone 6 with AT&T?

Ok so i have the plan that is the
30GB mobile share value
its me and my families shared plan with four devices on it.
after 12 months of payments for the phone you are eligible for an upgrade but you must turn your old phone in because with just 12 months of payments its not fully payed of yet so you have to turn it in. My phone doesn't have a cracked or shattered screen at all but the top and bottoms do have some chipping but you only notice if you look closely but -
there's nothing too noticeable about the phone so if the worker doesn't look close enough they won't notice but in the corner the screen is very slightly able to be lifted up if you use enough force but once again not noticeable- but will i still be able to upgrade? Will they still take my 5s if i turn it in so i can get the 6?

No, you can also choose to pay off the remainder of the balance on the spot and keep the device. You don't have to trade it in at all if you don't want to. They didn't take my 5S when I upgraded early and switched from contract to Next one year into my contract.