Hello Jorgem,
Welcome to the community!
I apologise for not coming across your post sooner. I understand you opted-out of Fido Roam. However, that is not the same as blocking roaming. Opting out of Fido Roam would mean that any usage would be on a pay-per-use basis. The charge you note corresponds to the data pay-per-use rate in the US (see here).
Roaming charges will incur when you use your device to make or receive a call, send a text message or use data while abroad. (see here). 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.
That's why I often suggest to others to disable any MMS auto-retrieve settings on their phones. You would then receive a SMS notifying of a MMS (no charge) but the data contained would not download automatically. You could then choose whether or not to download the associated data contents. You should also note that, with the exception of Wifi-calling, MMS does not generally get transmitted via Wifi. Downloading MMS while connected to Wifi would likely incur roaming charges. That said, if your device is supported for Wifi-calling, some types of usage would be considered roaming.
I understand you had disabled data on your phone. What phone do you have? You should note that some phones might consider certain system or MMS data differently from user data and continue to allow the former usage despite data and roaming data settings disabled. There may be additional phone settings to disable system and MMS data. To ensure unintended data usage, you might consider enabling Airplane or Flight modes for the duration of your trip. You could manually enable Wifi when required. I understand those modes would also prevent receiving SMS, however, you would need to know how your phone behaves in order to prevent unintentional data usage.
If your phone transmits system or MMS data despite disabling data and roaming data, you should note that you may also incur roaming charges with the other providers as well.
Hope this helps 😀
Cheers
