Iphone 4s from AT&T - want to use with PagePlus

[iMore Question]

Hi there! Here's my story: I've just been given a used Iphone 4s from a relative. It's an AT&T phone which will be unlocked once I get the code from her. I currently have Page Plus service with my other phone. AT&T told her that I would be able to use Verizon service once the AT&T phone is unlocked and if I get a Verizon SIM card put in the Iphone. Is this true? I'd love to stay with Page Plus if possible so I don't have to switch carriers and port my number. I've read so much online with conflicting information, I'm at a loss. Please help!! Thank you!