Call or send an e-mail to C&A (their info is on the RC web site). They will usually accomodate you and get for you sooner. Just tell them that you want to book a cruise and want to give it to your T/A.
BTW if you book a next cruise option while on board you only have to put down $100. initially and you get OBC...

You don't have to choose a cruise right away. When you book your next cruise you will pay the remainder of the deposit. We did this on our last cruise not knowing when we would take the next one. They will give you a confirmation number, then when you book the next cruise, you use that number as yor reservation number.