Flash iPhone 4 to different carrier?

I don't need any answers telling me why I shouldn't and such all I wanna know is I've never done it before but was asked to I'm trying to flash an iPhone 4 to page plus or boost or any other prepaid service I know it's possible I just need a Lil push in right direction to get done if anyone can help, phone is not jailbroken has good esn

Thank you

Take the phone to the company and tell them you want to do it. Usually they charge a fee around $15 or so to get it flashed, I know Cricket does it for sure.