How can I flash my Cricket Galaxy S4 to another CDMA carrier like Verizon?

[AC Question]

I bought a Samsung Galaxy S4 (SCH-R970C) from Cricket a year and a half ago, and now they're telling me that my phone is locked and I have to fork out another $500-$600 for a working phone. After doing some research, I've discovered that if you root the phone, you can flash another ROM to it.

I'm asking if there is a way to flash my Cricket phone to Verizon, and if so, how do I do it?