Wifi calling/straight to voicemail

[AGB24]

I've just switched to o2 specifically for wi-fi calling as we live in the country and get very spotty reception.

All set up and (probably) working, but when I call myself at home to test, it sometimes works and sometimes goes immediately to voicemail. When this happens I don't even get a missed call alert, just some text sent to me instead.

Presumably the wi-fi calling is either not working, intermittent or not very good... I'm sat at my desk next to my router with a solid 70mbps, it should be able to handle a call

Anything I can check or test? Thanks

[AGB24]

Sadly not.

I spoke again to the support line and they said they'd 'reset it' and to try again in 24 hours. 

As before, and I don't know whether it was connected to the reset, it popped into life for about 30 seconds but then disappeared. It did it again a day later too.

So I've had 3 bursts of about 30 seconds now over the last week, but it never stays working.