I've been with Sprint on a "SERO (employee discount plan) for like, 20 years - transitioned to basically a similarly priced T-Mobile plan. Been off contract all this time. I'm getting a direct mail piece indicating entitlement to an iphone 13 Pro "On US" -(fine print/asterisk reads: "With 24 monthly bill credits when you turn in an eligible phone, Down payment required)" The flipside of the postcard says I'm eligible for this 'awesome phone ON US' "No Plan Change Required." Ok, so what's the catch here? Is this a qualified deal for me, with the latest used IPhone I'm using - an iphone XR - and does this not mean I can get this phone free and keep this grandfathered $35/month unlimited plan, no strings attached, no contract required? (just figured i'd throw the question out there before i get involved with customer support for answers). THANKS!