Roaming costs are available at https://ee.co.uk/help/mobile/roaming/roaming-costs > Canada.
The most cost-effective method will likely be the weekly pass which enables use of your UK-allowances (voice calls, texts & mobile data) in Canada for a single weekly price. There's further info on https://ee.co.uk/roamingrefresh - if you don't want to pay the 7day cost, then you just pay per-minute for calls, per-text for text messages - although mobile data won't work this way. It needs an add-on.
Whatever billing option you choose, make sure you enable the free roaming facility before leaving the UK - this ensures your phone has access to Canadian networks and thus has coverage abroad. Text ROAMING to 150 from the UK.
