Hello Karen970,
Welcome to the community!
Sorry to hear you've incurred unexpected roaming charges. However, 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 you wish to keep your line available for emergencies, there is unfortunately no 100% guarantee your device won't use other services and trigger roaming charges.
That said, you should note that disabling data and roaming data does not prevent roaming for voice and messaging. It is generally recommended to enable Airplane and/or Flight modes to prevent unintended roaming usage. You could then enable Wifi when required. Had you enabled Airplane or Flight mode on your device? If you had, WhatsApp would not have been able to transfer the call to use cellular services.
If you had used 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 also note this forum is community-driven and not intended as a venue for customer services. We would not have access to your account. If you would like discuss your situation, you would need to contact customer service . In addition, they can also be contacted via Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Hope this helps 😀
Cheers
