I owed them money so billing came looking for me. after I paid them, the email address that sent final bill to me when I requested it was disneyresorts@disneyworld.com
Also looking at that bill it said this: “Thank you for choosing the Walt Disney World Resort! For billing inquiries, contact Guest Services at GUEST.SERVICES.BILLING@DISNEYWORLD.com OR 407-828-5630”
May be a fluke but I noticed I got through to them much quicker when I owed them money so maybe try that number or email addy might be faster