If you're using a DVA to pay for a cruise, you do the initial booking with the TA and then you have to call a special number at DCL in order to pay.
I don't know how Costco works, but for me, my TA made the reservation and held it, then I called the number to apply my DVA balance for the deposit. DVA's special # for DCL payments is 800-511-9333
Does Costco put your cruise on hold? If so, you can just put it on hold, then call the number above to make the deposit.
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