Why won't my iPhone 4S work with Straight Talk?

Okay so the first thing is. YES, it is a Verizon iPhone and I know they aren't supposed to work with Straight Talk.

-I called straight talk and the guy I talked to on the phone said all I had to do was the Bring Your Own Phone process. So I bought the 60 dollar package at Walmart with the compatible sim cards and everything else, but nothing is working. I have a straight talk phone as of now, and I got the iPhone from a friend. I really need help with this because it is seriously frustrating! Is there anyone who can give me Straight up Directions?

Go on wind