Default Was just given this phone

I was quite excited as I am using a really ****ty phone, but upon starting the phone I realized it was on the sprint network, which gets very unreliable service where I live.
My main question is, is this phone, the LG Optimus G for sprint, capable of switching over to another phone carrier? Preferably Verizon prepaid or Straight Talk as they both work extremely well in my location. If it is, do I need to root the phone? The last phone I rooted with a Motorola Triumph on Virgin Wireless, and it was beyond easy.
I have also called both providers, Verizon and Straight Talk, both were very unhelpful

If its not usable, the phone is for sale to the first person with 75$ in the four corners area, usa.