I bought a UK addon but it doesn't work. My son is in the UK and I can't call him.

Maybe you should contact Support
08:00 to 21:00 week time and
10:00 to 18:00 weekend
CHAT
Go on this page https://fizz.ca/en/contact-us
if you are not connect login then
Wait 15 seconds for the bubble icon to appear at the bottom right of the browser and click on the icon
FACEBOOK
Your can also send a message by facebook
https://facebook.com/fizzca and click send a message (this is a bit slow)