Hello Evanyiliu,
Welcome to the community!
I can understand receiving that Fido Roam welcome text message can be concerning if you had not intended on using the service. As Original_Lucy alluded below, merely receiving that message does not necessarily mean you've incurred roaming charges, only that your device had connected to a foreign network. I was able to confirm that fact here.
Fido Roam charges will only incur if your phone uses services -- make or receive a call, send a text message or use data abroad. It should be mentioned that while receiving SMS would not incur the roaming charge, any 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 further be noted that iMessages and RCS messages are sent (and received) as data and not as text messages (SMS).
As far as I am aware, having calls go to voicemail and/or rejecting calls to send them to voicemail should not incur roaming charges (see here). However, checking your voicemail would be considered roaming as one must call the voicemail service.
While unanswered calls would not incur roaming charges, it would be important to note that if your device used data when it connected to the foreign towers, that usage would incur those charges. I understand you might have not intended on using roaming data. However, some devices have been known to use data despite data and roaming data disabled (see here). As you have already done, it is usually best to enable Airplane or Flight mode in order to prevent unintended data usage.
For completeness sake, 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. 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 did not wish to use Fido Roam, you would need to opt-out of the service. In doing so, any usage abroad would be on a pay-per-use basis. You can view those rates here. You should note that this forum is community-driven and not intended as a venue for customer services. If you would like to opt-out of Fido Roam, 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
Hi there @evanyiliu , that's a great question. When in another country receiving unanswered calls from Canada do not necessarily trigger roaming charges. The message for roaming when your device is trying to connect to a local network is letting you know that your device is available to roam and if you haven't made a call or sent a text or accessed data, there won't be any charge. To be safe, I always remove my sim card and keep it in a safe place until I'm come home. Even a text with a link or picture is accessing data.
