We've yet to hear again from the OP. It does read like he was already set on getting another phone but may have been hoping for help that would allow his continuing to use his old phone. Who knows?

Not knowing what "KitKat" meant with Android, I suspect that the notion of his trying a technical solution such as installing a recovery and replacement firmware would have been a tall order.

Without his getting back here for any clarification, everything now would be speculation on our part. I have a little bit of idle time and so I'll add some of mine: Maybe he ran out of storage for installing and running apps on his phone?

Still, from what I see about the S3, these come with a minimum of 16GB storage. This should be enough for apps unless it never occurred to him to install an SD card (micro-SD presumably) for pictures, music, videos and other user data that one might accumulate. Getting one may be the simple solution that he wants and needs.