The Disney phone lines have been swamped for days - it isn’t just today. Disney needs to hire more cast members to handle all the cruise cancellations and rebookings. It isn’t fair to those of us who need to get thru to cancel before a deadline or make a payment before a deadline. This is Disney’s fault for not being able to handle the demand on their phone system.
I understand your frustration and am not a DCL apologist, but what could Disney have done? They would have had to know several weeks ago that cancellations/changes would be offered for a huge number of sailings, then find and train employees. I do not know, but I would guess that DCL probably has as many people as possible manning the phones right now.