Can i upgrade to new iphone 5s even though i upgraded in february?

I upgraded to the Samsung Galaxy s3 in February of this year and It doesn't even work anymore. We have sent it off once to be fixed but they said I can't send it again because it isn't the phone, i've done something. But I always use a case and everything. I want to get the iphone 5s or 5c but how can I if I just upgraded? Please Help me! It's greatly appreciated! Also, I'm with ATT & they aren't very cooperative!

Go to your att account and look for the upgrade option.
maybe they will ask for some money and iff you have good credit they will give it for free.
but most likely you have to pay.
instead of talking on them, chat with them on their website.
less attitude from them, i know they are horrible. I had them but got rid of them.