Have you already had the chance to speak with one of our agents to have this looked into?
To clarify, the automatic message you receive is simply a welcome message to inform you of the applicable charges at your current destination. It does not mean that you've been billed. On our end, we will only charge you if there is usage made while roaming using your Fido SIM card. That is the only way we can track a communication to your device. Billed usage are calls (incoming and outgoing), sent texts (incoming are free), and mobile data.
However, since you live near the border there are some solutions we can suggest: