Mobile Networks setting crashes phone

[darkness1111]

All of my detailed information is listed below. My problem is that I have a Sprint Samsung S3 activated through Cricket, which I purchased unlocked on eBay. I took it to my home store and they activated it. All works fine except my picture messaging. Initially I was receiving duplicate messages, I found that I had two messaging programs installed and once I removed the extra program, the duplicate messages ceased, however that did not resolve the picture messaging problem. I cannot send or receive them and I found through a google search that the resolution to this problem is to access more settings >> mobile networks >> and do something like "allow package data." My mobile data settings are on, I am disconnected from wifi, and within the messaging settings, all mms related settings are enabled. When I go to more settings, and select mobile networks the screen doesn't move for a second, then it goes black, the screen freezes and the phone restarts. I am wondering if there is anyway to debug the OS itself or if my only option is to do a factory reset.

I'm also considering installing a custom ROM, any suggestions?

Model number: SPH-L710
Android version: 4.12
Baseband version: L710VPBMD4
Hardware version: L71014

Let me know if more info is needed.