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Fido will only charge roaming fees for actual usage on a foreign network. That is, when you use your device to make or receive a call, send a text message or use data while abroad (see here).
An alternative method to prevent roaming fees would be to enable Airplane or Flight mode for the duration of your trip. You could manually enable Wifi when required. When using this method, you should note that certain Wifi-calling usage would also be considered roaming. In addition, there have been some instances where the Airplane or Flight mode settings do not function as intended so you might consider testing the functionality of your device before attempting this method.
If you removed the Fido SIM card from your phone, it will not be able to access any mobile network so you would not get charged roaming fees. That would also include not being able to access Wifi-calling.
Hope this helps 😀