Ice Candy Studio review: Inappropriate Booking 1

I just want to share my experience with Ice Candy Studio (Photography Service http://www.icecandystudio.com) I send them an email last year and continuously provide updates on when we will deposit our downpayment. Based on our email conversation, he agreed that we make a deposit on Feb or March of 2014. (Please check the thread below)

Today, I send them an email asking them for their bank details where I can deposit our down payment but received a reply that they already gave it to another client. I was shocked and I felt that my right as a consumer was violated. I know that they have a first come, first served basis but I think its still inappropriate to simply give out our pencil booked date to another client without informing us. I trust Ice Candy Studio's word that making a downpayment on Feb/March this year is ok with them, meaning, they will prioritize us and in case someone wants that date, they will inform or ask us for confirmation.We already released our propose budget and we may have a problem because of this (Budget with Photo and Video Coverage)

May I know if I can file a formal complaint about this?