Hello 1027-d,
Welcome to the community!
Sorry to hear you've incurred unexpected roaming charges. I understand you might not be currently using the device with your Fido SIM card. However, is that device with you in Spain? If it is, has the device been off for the duration of your trip?
It is generally recommended to disable data and roaming data when abroad to prevent unintended roaming usage. However, since some devices might still use data with those settings disabled (see here), it is further recommended to enable Airplane or Flight mode for the duration of your trip. If you do not wish to use the device at all, keeping the device off at all times while abroad would also prevent roaming usage.
The Fido Roam charge incurs when your device uses Fido Services abroad. That is, the charge will incur when your device makes/receives calls, sends text messages or uses data outside of Canada (see here). The mobile providers only know usage. If a device is using services when its settings are set not to use them, that's an issue with the device. The mobile providers have no access to a device's settings to know what settings are enabled/disabled. If there was roaming usage on the system, your phone apparently connected to the local networks and used services.
If you device and plan are supported for Wifi-calling, you should note some usage is considered roaming. There seems to be some misunderstanding regarding Wifi-calling. I'm not sure how people have gotten the impression that Wifi-calling does not use the networks. However, that is not true. While the calls and messages do not transmit via cellular towers, they still use the networks via the internet gateway (see image here). The cellular towers and Wifi are merely alternate means of accessing the networks. Calls and messages would not be able to complete or get sent/received without the networks. As such, using Wifi-calling is technically using Fido services. However, they have allowed certain usage to be free from additional charges. All the messages and calls you receive (from anywhere in the world) will be taken from your plan's voice minutes and messaging limits. As well, all Wifi-calling messages and calls you make to a Canadian phone number while abroad won't incur long-distance or roaming charges (see link above).
You should note these forums are community-driven and not intended as a venue for customer services. If you would like to discuss those charges, you would need to contact customer service. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Hope this helps 😀
Cheers
