Switching a new phone to a line other than the one it was intended for
I bought my daughter a new iPhone 13 for Christmas, but it turns out she really likes her old phone and doesn't want to upgrade yet. Meanwhile, my husband's phone is quite old and he is definitely ready for an upgrade. We're all on the same plan, obviously. I ordered the phone through ATT.com as an upgrade to my daughter's number, but both she and my husband are eligible for upgrade. I'm already paying the installments on the new phone.
Rather than return the phone, I wondered if I could have my husband activate it on his number instead. Is this something that I need to ask AT&T to do, and if so, WHERE? I don't see an option in my online account. Maybe I need to take the phone to an AT&T store and have them do it? Has anyone done something like this before? Any help appreciated.