Tmobile offered a free upgrade from an iphone 7 to iphone16? Too good to be true?

Hello, just wanted to check this. My dad is using an old iphone 7 on one of my line. I was calling in to do a sim swap since I just bought a new phone, when the person on the line told me that there was a promotion to upgrade my dad's iphone 7 to an iphone 16. Free, except I just have to pay sales tax, and trade in the old phone.

Is there any catch to this? The rep told me this was a "once in a lifetime deal" and was really sort of pressuring me to take this deal. I want to but I just want to double check I'm not being trick somewhere lol