In the same room, I've tried from about 1 to 4 meters away from the Nest Audio. If I try to specify "call [contact] on phone", the speaker responds that it is making the call then immediately states there was a glitch, try again later.
When I got the speaker, it was with an expectation that there would be some way of actually making calls through the speaker - at least to be able to use it as a Bluetooth speakerphone. I got it for my recently vision impaired mother, who had just learned to use the assistant on the phone to make calls with "Hey Google, call [contact] on speakerphone." So it was a huge disappointment when having the Nest Audio nearby broke this functionality instead of enhancing it with a better speakerphone feature than the one in the phone. The "just invoke the Assistant manually on the phone" advice in the FAQ does not work well for someone who struggles to even just unlock the phone.
I suppose that with US and Canada covered by a working service, there is not that much attention on making calling via Nest work in smaller international markets. I've seen some leaked info on a "Nearby calling" feature that would have made this work, but seems to have been abandoned. Unfortunately there seems to be no open API for making a voice communication service work with the Nest - only case of third party seems to be Zoom. Thus the only option I would have for developing a workaround to use the speaker for calling would be to make some sort of Google Meeting to phone service bridge.
For just making the speaker able to initiate the call on the nearby phone, I'm thinking I might be able to do a workaround by making an Android app that can somehow initiate a call in response to a request to the Google Home Assistant, for instance by hosting a virtual matter device for each of the contacts it can initiate calls to.
