How does the Iphone $830 deal work with Boost Mobile? Is it for new customers only?

I need a new phone since my 5 year old one is having screen issues. I saw that Boost Mobile has some kind of deal where if you go with their $65/month plan they apparently pretty much give you a free Iphone 17? Given that I currently pay them $25/month for my current plan this seems like a pretty good deal since the extra $480/year I'd be paying is probably less than it would cost me to get a new phone anyway.