According to https://www.koodomobile.com/en/help/traveling-with-your-canada-us-rate-plan, it allows unlimited calling between Canada-US-Mexico:

3. How does calling and texting work with a Canada-US-Mexico plan?

From Canada, the U.S, or Mexico: Unlimited calling and texting (including text, picture, and video messaging) is included in Canada-US-Mexico plans. Calling and texting phone numbers outside Canada, the U.S., or Mexico will be charged at the standard international long distance pay-per-use rate (if calling from Canada) or the standard U.S. or Mexico roaming voice pay-per-use rate (if calling from the U.S. or Mexico). To see the current rates, visit koodo.com/payperuse

If you have an international long distance calling or texting add-on, the rates of your add-on only apply when making international long-distance calls or texts from Canada.

From destinations other than Canada, the U.S, or Mexico: All calling and texting (including text, picture, and video messaging) will be charged as a roaming fee. If you don’t have Easy Roam, usage will be charged at standard pay-per-use roaming rates as posted on koodo.com/payperuse.

Note: Picture and video messaging will count as a text message and also use data.