Is this on your bill? 

Or you got a notification when you are close to the border?

Let me flag a rep for you.

To avoid this from happening again, make sure to manually select your network to Koodo, so that your phone does not automatically connect to a nearby U.S. cellular tower.

Hi ​@ricci 

We have reviewed the details and we have been able to remove the roaming charge for the line ending in *04 since it was triggered due to accidental data roaming, feel free to check the details in your self serve account when you get the chance.

For more info about how to prevent accidental roaming charges, please check out this article https://community.koodomobile.com/plans-services-232910/easy-roam-understanding-how-you-will-be-charged-while-traveling-7811296