There is some point below related to the WestJet Change Flight for your help:

1. You need to pay about $39-94 if the changes are done before the 60 days of departure for all destinations except Europe. 
2. However, travellers need to pay about $94-319 for the flight changes done 60 days after the flights between Canada & Europe. 
3. Moreover, you need to pay about $90-99 for the changes done within 60 days of the departure towards the destination, except in Europe. 
4. On the other hand, you need to pay about $94-199 for the bookings modified within 60 days of the departure for all the flights between Canada & Europe.
5. However, if the new fare exceeds the original fare, you can pay for the changes. It’ll be done if you make the changes after 24hrs of the booking. 

Conclusion:

Therefore, we have provided you with all the respective details about the process to change the flight with WestJet Airlines.