Unsealed iPhone 15 with WiFi issues and email address confusion

Husband bought 15 for Christmas 2025, walked in T-Mobile just handed him an unsealed iPhone. Joint account, all my data in employees data. Sent back & told nobody entered name or phone number! Then went to Apple tech. Support told him wasn’t working right on WiFi. They turned WiFi off

am I missing something? Didn’t trade in iPhone 8+(256).

never had service like this. Surely diagnostic tool to immediately diagnose problems.

box to iPhone wasn’t sealed do I have a problem phone that nobody tagged as bad?

I’m good at tech info, did I go from 8.+ to 15 to quick?

I’m ready to sell it. Sick of not communicating as always did!

suggestions welcomed!

thanks

k

[Re-Titled by Moderator]