You have to call DCL and ask them. They may have to get a supervisor to make the decision. There have been reports where DCL has extended payment dates, but not a lot.
Another option, depending on the amount and if you used a TA, would be to see if they could temporarily cover you and you could pay them? Of course if DCL extends it you are golden. Good luck and hope everything works out for you.
If they won't let you extend you final payment, would you be able to change your reservation to some future cruise? You should be able to move any existing cruise payments to a new cruise date and give you extra time to make final payments. If this was something booked onboard a previous cruise, there may be issues if you need to go past the 24 month window for cruising.
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