Xbox app gamertag

So basically i changed my xbox name a few months ago to and on the app it showed this name but a few weeks ago it started to show my old name for me and other people but only on mobile notifications.

i’ve tried logging out and back in and this works but when i go to my account to for example change my gamer picture it changes back to my old name.

does anyone know a solution or know why this is happening?

:)