Hello Ankitdoshi1,
Welcome to the community!
Unfortunately, it does not appear their account customer service lines are open on Sundays (see here). While they can also be contacted via Live Chat, Facebook, or Twitter, those avenues also appear to be closed on Sundays.
If you did not wish to use the feature, you would need to opt-out of Fido Roam. In doing so, your usage would be on a pay-per-use basis. You can view those rates here. You can also request a roaming block on your line. That block should prevent any usage on a cellular tower abroad. It should be mentioned, though, as far as I am aware, that roaming block would also prevent devices from accessing extended coverage in Canada (Fido-EXT). You would also need to be clear as to which option you choose as there have been instances where people have thought they blocked roaming (no usage abroad) but only had opted-out of Fido Roam (pay-per-use abroad).
The Fido Roam charges will 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. Disabling MMS should prevent that data transfer. Though, it should further be noted that iMessages and RCS messages are sent (and received) as data and not as text messages (SMS).
In order to prevent unintended roaming charges, it is generally recommended to disable data and roaming data. However, you should note that disabling those settings does not prevent roaming for voice and messaging. In addition, some manufacturers might allow some data usage to occur despite those settings (see here). That's why it is also generally recommended to enable Airplane and/or Flight modes in order to prevent unintended roaming usage. You could then manually enable Wifi when required.
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). As far as I am aware, disabling roaming does not prevent Wifi-calling usage abroad and therefore could still incur roaming charges.
You should note the forums are community-driven and not intended as a venue for customer services. If you wished to discuss your matter and/or opt-out of Fido Roam, you would need to contact customer service
Hope this helps 😀
Cheers
