Under GSM it says Calling via 4G disabled; is this correct?

Yes, that’s possible. Indeed, when using Octalarm Connect (via the SIM card provided), VoLTE (calling via 4G) is often turned off because it was not supported by KPN until the end of October 2024.

If you use a proprietary SIM card, this setting depends on the telecom provider and/or type of subscription.

Good to know: the component must be on to alert via VoLTE (calling via 4G).

This is resolved as follows

Turn on Calling via 4G.

See Settings|Interfaces|GSM: Customise GSM settings for further explanation.