Who are you peolpe - bunch of sheep? Mindlessly following the "dear leader"? Of course, a lot depends on what rules you think applies. But generally, you do not have a contract with Aeroplan.The $100 charge on your AT&T account is illegal. The fact that you did not turn on the "airplane" mode does not authorize anyone to charge you anything. Do you think that you form a new contract with Aeroplan just by keeping your phone on. A contract requires "meeting of minds", but since you do not have one (as evidenced e.g. by not turning the phone off) how can the "meeting" occur?
And secondary - to all those who scold you for not turning the phone off. There is no technical reason for that rule that is needed for the safety of the airplane. If you are on the airplane that can be affected by the telephones - you better get out quick - and never fly that airline again. The only reason to introduce that rule in the past was to do not disrupt telephone networks on the ground, as the fast-moving telephone signals could put too much stress on the ground-based telephone towers. But, truth be told, other equipment, like old tape-based video cameras, do generate signals capable of influencing instrumentation of the older avionics - if you use it close enough to the cockpit (e.g. in first or bus class).