My iphone4s has ios 7.0.4 crashes and will not let me connect to wifi

On december 26th, I was having trouble with my wifi connection. I was on the phone with someone and my phone completely shut off and restarted itself. I checked to see if I could finally reconnect to the wifi but it was grayed out. I tried different things like turning the phone off and on, resetting the network settings and turning the wifi off and turning it back on (When it was not grayed out) but it just made my phone would crash even more and for a while I wasn't able to read texts and whenever i went to turn on my wifi it would either freeze, crash again or it would load the networks or the wifi would still be grayed out. If anyone is having trouble like I am, please let me know.

P.S. This a replacement phone that I had just bought bout a month ago. The last one had similar problems and stopped working completely. I'm hoping this is not the same problem.