Hi, Carolyn!
I've booked several dining reservations for March and needed to supply my credit card in order to hold some of them. However, my credit card has not been charged, and will only charged for that reservation should I not cancel my reservation yet fail to show up on that day / night.
If you decide to make a reservation which requires you to pay the full amount at the time of reservation, then this amount will be retained if you fail to honor your reservation and are "unable to cancel the reservation at least one day in advance." Take a look at these
Frequently Asked Questions regarding Dining Reservations for more information.
We often add our Dining Plan after we have made our Table-Service reservations, at which point I simply call (407) WDW-DINE and tell the Cast Member at Disney Dining that I've now added the Dining Plan. If there is a credit card guarantee on the reservation, that same policy will apply ($10 will be charged per person if the reservation is not honored and I fail to cancel at least one day in advance.)
Should you need to cancel a reservation, call (407) WDW-CNCL or visit the Table-Service restaurant podium or the front desk concierge at any WDW Resort hotel.
Again, take a look at those frequently asked questions, as they'll put your mind at ease about many Dining reservation questions. Of course, come back here with questions, too, as we love to help Guests make the perfect plans for their Walt Disney World Vacations! :-)