This is probably a reach, but...Perhaps you're trying too soon to change the booking online, like within 12-24 hours? (Of course, that blows any '24-hour grace period' possibility out of the water...) For instance, American Airlines doesn't even email your booked itinerary/paid reservation until the day after you've booked it. If you don't know that, it causes quite the panic. 'Oh, no!!! Where's my reservation?!?'
Have you looked all over their website for an email address/different phone number, such as lost and found, luggage questions, etc.? Maybe that would get your foot in the door. Have you tried Googling 'Canadian phone number RyanAir', etc.? Sometimes there are phone numbers not published, but consumer reporter-types find them and print them online :-)
Let us know how this turns out, and good luck.