Hello, John Simon.
Using someone else's account is not welcome, and users are banned in almost all games. In your case, try contacting Minecraft support directly by filling out the form on the page: https://help.minecraft.net/hc/en-us/request/new?ticket_form_id=360001225811 and describe the problem. It is possible that they will meet you halfway and cancel the ban. If the game support recommends contacting Microsoft (since we are talking about the Dungeons edition), then contact the chat on the page: https://support.xbox.com/en-US/help/games-apps/game-titles/minecraft-info