I know WestJet has been having reservation centre issues, in light of the new system changes. For those with major issues, travel vouchers are being offered - so WJ is trying to please.
When it comes to itin changes - a lot has been due to changes at Pearson and a couple other major airports. Nothing WestJet can do, accept modify their flight plans. Annoying for travelers, but A/C regulars have been complaining too... such is life with air travel.