Hello,
To call or text between the two Canadian phones you need to use either +1 yyy xxx xxxx or 00 1 yyy xxx xxxx, where yyy is the Canadian area code.
In regard to roaming and charges. I am not familiar with the plans offered by your provider. Generally, in order to use a cell phone abroad, either for texts or phone calls, you need a roaming plan. So you can’t avoid roaming charges if you want to use your phone abroad.