Hello BarryBonz,
You should note that merely receiving that Welcome Abroad message does not necessarily mean that your device had used services. It's an automatic notification to inform customers that the device connected to a foreign cellular tower, not that usage had occurred. I was able to confirm that merely receiving that message does not incur roaming fees (see here). However, if you do incur roaming charges, it's likely your device used other services when it connected to the foreign network.
The Fido Roam charges will only incur if your phone uses services -- make or receive a call, send a text message or use data abroad. While receiving SMS would not incur the roaming charge, it's worth mentioning that the data contained within MMS (incoming or outgoing) would be considered roaming data and charged accordingly. You should note that MMS are not solely restricted to pictures or video messages. Messages with subject headers or group messages etc are also considered MMS. It should also be noted that RCS messages are sent (and received) as data and not as text messages (SMS). Even if a received text message is SMS, if a device is configured to provide Delivery and/or Read receipts, those would be sent as SMS or data and considered roaming usage.
In order to ensure there are no roaming charges, you would need to ensure your device does not use services abroad. The mobile providers only know usage, they do not know what settings may or may not have been enabled/disabled on a device. No usage abroad, no roaming charges.
In order to prevent unintended roaming charges it is generally recommended to disable data and roaming data. However, it should be noted that disabling data and roaming data does not prevent roaming for calls and messages. In addition, it should also be noted that some phones might consider certain system data differently from user data and continue to allow the former usage despite data and roaming data settings disabled. For example, while disabling data and roaming data should prevent data usage on foreign networks, some mobile manufacturers (ie Apple) does seem to allow some data usage despite those settings disabled (see here). That's why in order to prevent roaming charges, it is also usually recommended to keep Airplane or Flight modes enabled for the duration of trips. Customers could manually enable Wifi when required.
For completeness sake, though, it should be noted that while using Wifi for regular internet access will not incur Fido Roam charges, there seems to be some misunderstanding regarding Wifi-calling. Some Wifi-calling usage abroad is considered roaming. 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).
If you do not wish to use Fido Roam, you would need to opt-out of the feature. In doing so, any usage would be on a pay-per-use basis. You can view those rates here.
You should note these forums are community-driven and not intended as a venue for customer services. We would not have access to customers' accounts. If you wish to opt-out of Fido Roam, you would need to contact customer service. I understand you are currently outside of Canada. They do provide a number to call From Abroad. Calling that number from overseas would not incur roaming charges when called from your Fido SIM (see here). Alternatively, customers should also be able to call that number collect from a landline.
Hope this helps 😀
Cheers
