The reply is the same as always: yes, you can.
I am in the same situation, Ive got two photoshoots for Sigourney that I would like to refund and buy two Diamond Passes instead, can you tell me who I should contact regarding this and should I buy the two Diamond Passed asap then worry about the refund for photoshoots later ? Thanks :)
The process for this is you need to purchase your diamond passes and then send an email to the shop with your photo order details I.e. Name, order number etc and they will refund you, please do bear in mind though there is a large backlog of emails so it may be a