iPhone 16 Pro Max Volume Up & Down buttons not working in Lockdown Mode

My iPhone 16 Pro Max I bought a week ago took me 3 days with a T-Mobile rep to set up because I move from android to iPhone. Yesterday the volume up and down button stop working when the screen is in lock mode and I can't seems to figure it out. A T-Mobile rep has been trying to assist me via chat and we are just not getting anywhere. Also at night when it starts to get dark the phone Always on Display shuts off to a black screen ughhhh. The rep was planning on trying to get me a refurbished phone and I told them that their policy is bad because if I'm paying for a brand new phone and there's some malfunction or any other issues I should get another new phone anything beyond that would yes be a refurbished. Anyway we found an option that we look at and hopefully it will work tonight but the Volume Up & Down is my issue and wondering if anyone else have that problem. The button works fine to do screenshot and power off the phone so I am not sure why the volume thing stop working.

[Re-Titled by Moderator]