We cannot exchange one guest for another online because we do not store payment information on our server but you can use your ticket as credit towards other purchases on our checkout page! Simply add the desired new product(s) into your cart, go to the checkout page, and click on "Exchange Ticket". You will need the ticket code starting with a T- from below the QR code of your ticket. Be sure to use all of your credit in one session/transaction, as any amount left over will be forfeit and you will not be given a partial refund nor will you be able to use the leftover amount for other purchases after you check out.
Alternatively, you can always use your photo op as credit towards the purchase of a new photo op at the convention if the desired session has not sold out.