Old and New gamertag showing on same account

New one is "" old one is "immune2sound"

Recently, I created a new gamertag on the xbox 360. Now when I access my account on the xbox app and the xbox one it shows both my old gamertag and the new one. At first login on the app it says welcome (my new one) but after that it just displays
my old one and the new one underneath. Also my friends only see the old gamertag instead of the new. I would like it to only have the new one - . Is this a bug or...?

It's only been a day so I don't know if I just have to wait for it to register or something but any help is appreciated.

I spent money to get the new one so I hope I will be able to use it.

:)