samsung fail to repair samsung galaxy s4

my samsung s4 galaxy needed to go in for repairs for a cracked screen. at first when the screen cracked i was not able to take the phone in because the closest store from hazyview is nelspruit about 70km, so i kept it and used it as it was still in 100% working order. when i gave it in for the \free"screen replacement they phoned me back (the store ***) and refused to replace the screen as they call it \"" screen abused\"". yes the screen is totally cracked and some dirty spots between the cracks but that is because its been used daily as a working phone.....why do they give a free screen repair with this phones in the first place if they want to come with excuses? whether its a small crack"