Keep contacting Air Canada. Under Canadian law an airline must rebook you in your ticketed cabin on their next available flight or on any airline if they can't get you out on in your ticketed cabin.

There might not be seats available but usually they open up. If there are J seats it is illegal for an airline not to book you into them if you originally had J seats.

Make sure you get a printout of the law ( CTA passenger bill of rights) bring it with you to the counter and insist they respect the law. Looks like there are flights available. The agents are well aware but sometimes don't care. This is the the CTA needs to start imposing massive fines against airlines as well as employees who refuse to obey the law.