I agree with exAC. Unless you have been authorized in writing to have access to your friend's Aeroplan account, no AE agent, SE or Elite, can do what you want them to do. How would you feel if you found your ticket had been cancelled by someone else who claimed to an SE agent that you didn't want to travel.

And I fail to see why you should not be charged the cancellation fee for your ticket as you are not the person having jury duty, nor it appears, even a legal partner of the person.