If the OP is from Cartersville GA., the GA. policy is as follows:
Campsites
Reservations can be changed one time without penalty, provided that a 3-day notice is given. Any additional changes will incur a $10 transfer fee (per reservation). Full cancellations made at least 3 days prior to arrival will incur a $10 cancellation fee. Any changes or cancellations made less than 3 days prior to arrival results in a loss of deposit. (Note: Visitors who have paid more than the minimum required will be refunded all but the required minimum deposit amount.)
found here:
http://gastateparks.reserveamerica.com/resource/contracts/ga/CancellationPolicy.html