We cannot exchange one guest for another online because we do not store payment information on our server.
We would have to refund the one photo op ticket and you would need to purchase the new one. Please keep in mind our refund deadlines which are displayed on the Info tab on our online store for each convention. We are unable to process refunds after the refund cut off.
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.