I'm looking at a RT to Italy on Air Canada, and aircanada.com is giving contradictory information about whether any changes are allowed (either free or for a fee) on Basic Economy tickets. The first choice presented between Basic/Standard economy says both allow free changes, then after selecting flights it says that Basic Economy allows no changes at all. The definitive word on this is the underlying fare rule, right? But I'm not confident that I can interpret the nuances of the way it's written. Recommendation on how I can get a definitive ruling on this before booking?