AT&T Business users now get unlimited calling to Canada & Mexico

For AT&T business users on the Mobile share value plans (shared data)

FREE unlimited calling and texting to Canada and Mexico. If you are calling to other countries, contact us to add the $5 International long distance plan. It will greatly reduce the international long distance charges for your company.

Discounted international voice calling to 225 other countries.

https://www.att.com/shop/en/wireless/international/long-distance.html

https://www.att.com/esupport/article.html#!/wireless/KM1045615