I tried this twice already with a booking that I made directly with Princess online. When a new promotion comes out, I price the exact same category online, which comes lower than what I originally booked. But when I call or chat with Princess and give them the promo code, they aren't able to apply it to my existing booking. It has a refundable deposit so I just don't understand why they just can't reprice it like I have been able to do with Royal, Celebrity, and HAL. They can bring the price lower but not as low and with the same perks (onboard credit) as the promotion (Festive Days). There is nothing in the terms that states it only applies to new bookings. Anyone know how this works?