Utilizing Onboard Credit Offer AFTER Reservation

[BeeeJay]

I rec'd an email today offering up to $500 on-board credit on select dates. I checked my previously reserved cruise on NCL and it shows two offers ending this week:

 

Dash Onboard Credit: Receive up to $500 extra onboard credit based on stateroom category. Offer ends this week.

 

 

Holiday Cruises Onboard Credit: Book today and automatically get up to an extra $700 onboard credit on 2015 Holiday Sailings. Offer ends this week.

 

My sailing is December 13-20 Western Caribbean on Norwegian Getaway from Miami, in an M6 Mini-Suite, booked via NCL Casino at Sea, on an upgraded comp offer from Rivers Casino. I have paid the outstanding charges for upgrades, taxes, excursions, dining, etc already. I am in the 75-56 day period before my cruise.

 

My question is, will they allow me to add this promotion/rebook under it? Any advice for asking for this when I call? Would like to go in knowing the "right things to say" if there are any, and if that makes any difference. I suspect its a cut and dried situation, but thought I'd ask the experienced cruisers here, just to cover all my bases.

 

Thanks in advance!