Unfortunately, the deadline for requesting a Mutual Cancellation has timed out. You only have 45 days.
But on Monday, between 9 and 5, phone Customer Support. With any luck you will get one of the Utah customer service reps, who speak English as a first language (or at any rate, American) and may be able to help you.
With Canada Post, I have found phoning them is more useful than email or even your local Post Office. (The outlets are pretty useless since they can only refer your problem to Canada Post proper.) The phone clerks are in New Brunswick and are therefore very helpful.