Bother your travel agent if you want to get it done. I don’t believe NCL will work with you since you booked thru a TA. Mine called NCL and worked with them over the phone. The prices had taken a huge drop and I was able to upgrade several levels without paying any additional fees. Also, if you don’t want to upgrade your cabin, your TA can also request a FCC for the difference in price. I got a FCC for a cruise that was paid in full when the price dropped after final payment. I wasn’t interested in an upgrade on that one. Good luck.