WhatsApp runs independently of your cellphone service so you can use it without having to worry about extra international charges.

You will only get charged extra if you use your phone’s messaging/phone app.

@Allan M well, yes, mostly.

@Keith Keller WhatsApp runs entirely over data.  This means that if you call or video call another WhatsApp user from inside WhatsApp this does not up any of your airtime nor cost you any long distance charges; similarly, if you message another WhatsApp user from inside WhatsApp, it does not count toward your SMS/MMS bucket with Koodo.  

However, all activities in WhatsApp use data.  If you’re attached to a reliable WiFi network somewhere (e.g. at home, at your office, etc.) then Koodo is not involved at all.  However, if you’re away from a WiFi network (or using one with a weak/unreliable signal and also have certain feature enabled on your phone to switch to mobile data automatically to augment weak WiFi) then you will be using some of the mobile data Koodo gives you every month with your plan.  

Hopefully that makes sense.

That works, Allan, thanks.