Account Settings: Username Error : Updating Issue

I recently changed my username on twitter from @MajistiiMontes to @MajTheGr8. At first I seen my updated name but now however my name still shows @MajistiiMontes but when clicking it, it says "sorry, that page does not exist" and you can only pull my profile up by typing in my current name in manually with the updated name @MajTheGr8. I tried going back to my account setting to restore my original name but it says "thats you" in green text when i type it in as if its still my current username. Whats the problem?