Can a promo be added to an exisitng ressie?

[3DisneyBuggs]

Let's say I book a room now for August. Then let's hope free dining is offered- can I add the free dining? What if I had a discount on the original ressie? Can i cancel one discount for another? Or would I have to cancel one package and book a new one?

 

[TiggerPiglet]

I change my ressie's all the time. I orginally booked with AAA and then when the AP codes came out, I changed it. The only thing with the free dining, I don't believe you can use a discount, except AAA with that.