So i talked to a few staff in game and found out when you change your username in MC your claims stay for your old name and dont update for your new one.
So that’s why i need your help aha, im trying to get my castle back from my old name Feare_ and give it to my new name Swag_Jesus. If you could help me out i’d be super grateful 
What do you mean by claim? Do you mean chest/sign locks?
I mean my build, i made a castle and the entire claim is still owned by Feare_ and not by my new name Swag_Jesus.
I built a large castle but now after changing my name i cant build in it anymore.
Nothing is actually stopping you from building there. If you owned it when you had another username you still own it as swag_jesus
Although, if you’re talking about locked things like signs or chests you’ll need a staff member to unlock stuff for you