In June I booked a NRD cruise and then about a week later found that a much better deal was available via a TA group rate. Transferring the booking to the TA was possible, but at the booked price (not the lower group rate). To get the group rate, I transferred the booking, the TA cancelled it, requested an FCC for the $900 NDR, and then rebooked with the group rate. When the FCC was issued (minus $200 for a cancellation fee) the TA applied it to the booking. The savings was significant and included additional perks so the loss of $200 was well worth it. This was my experience but it was a few months ago so I'm not sure if it would work now.