You can schedule a callback using the automated assistant and ask the Rep to place you on the seasonal hold plan .

Note that you won't be able to use your line at all (not even receive text messages) and that you will have to pick an in market plan when you come back.

If you have no tab, you may want to consider changing to the 3G $15 starter plan.  It costs the same as the seasonal hold and you will be able to receive incoming texts (for 2 factor authentication).  You just need to make sure to avoid roaming

https://www.koodomobile.com/en/help/keeping-your-account-open-when-travelling

https://www.koodomobile.com/en/rate-plans?INTCMP=KMNew_NavMenu_Shop_Plans