Why does the touch on my iPhone 5s keep freezing?

So my screen was cracked for a little while and yesterday I got it fixed. Everything was fine for a while and then I tried to text someone back and the touch screen wouldn't respond. So I locked it then unlocked it and it was fine but then it did it again later when I was trying to go through my apps. I again locked and unlocked it and it was fine but this has happen quite a few times now. How can I fix this?

Its either your screen, or your cpu is getting maxed, send it in for a replacement

Restart the phone too see if any improvement. Delayed touch response is one of two things. 1. The phone is bloated and full and needs a little more processor room to follow commands. Do some house cleaning. 2. During a screen replacement they should also replace the digitizer (screen response sensor). Either not reconnected back properly or loose wire perhaps. Best luck.
http://www.repairsuniverse.com/iphone-5s-lcd-touch-screen-digitizer-assembly-replacement-white.html?cmp=googleproducts&kw=iphone-5s-lcd-touch-screen-digitizer-assembly-replacement-white