Tickets must be printed before they can be exchanged in a new order (seats map will show them with white text on orange if the ticket has not been printed)
If a season/show isn't printing yet see “exchanges/swaps before printing” lower on this page
The price isn't matching things to check
ensure the price type of the new seats matches the price type of the original order
make sure that the new seats are in the same zone as the original seats
check if different days of the show have different price points
the price may have changed since the original purchase, see a senior agent
Some shows have a promoter fee applied to all tickets, check with a manager to have the fee temporarily unlocked so you can waive them