In a three week period I got vouchers from two different airlines. One you could use on line and one where the process is as Paul described. You can also take the voucher to an airport ticket counter and take care of business there (which I did, quite successfully.) Still sitting on $500 from the other airline.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014