If you want to use a 1-800 # you can call 1-800-828-0228. It will take you through all the prompts finally telling you to press option 3. The other one I believe is 1-407-WDW-DINE to go straight to dining.
I keep the 1-800 # in the address book of my cell phone, in case I need to change any ADRs when I'm down there.