"Force", absolutely not. I would also suggest you drop that word from your questioning if you call them as well. There's a good chance they'll just do you a solid at nost cost if you're nice and explain the situation. If you "demand" or attempt to "force" I can guarantee they'll force you to pay a fat change fee if it's even available.

That said, I'm gonna assume you looked really closely at your booking and that the time didn't just change by like 5 minutes? I get those emails constantly from Aeroplan, I have a RTW booking that's changed multiple times, with no email, but my simple booking that has a 5 minute sked change results in an email.

I would also make sure to check your partner's reservation on AC.com to make sure it hasn't changed. There's a good chance it changed and an email was never sent/received/got deleted.

Assuming all of this stuff is correct, then your best bet is phone AP, let them know what's going on, ensure they know it was an "involuntary change" and that you'd like to be put back on your original itinerary. Hell, it may even work out in your favor where they rebook you into a paid booking class. If they can't/won't put you back on your old itinerary, then I'd have your partner get on the horn with that same agent and ask if he/she can be booked on to the same one you're on due to your involuntary change. Those are kinda the magic words to use, rather than uncomfortably ask "I'm not gonna have to pay for this am i?". Now if they won't do it for free, you could ask to escalate because they can do whatever they want for whomever they want, a supervisor could push this through if you appeal to their sensibilities.

Failing ALL of that, you could just suck it up and travel on different itineraries, or pay the change fee on your partner's routing to get back on track, not ideal, but I would think one of the above suggestions would work before getting to this.