Currently PSTN calling is a bit problematic as it doesn't seem to be available at all for organisations that do not have a billing address in the country where PSTN calling is available.
Our use case for pstn calling is to replace aging SIP PBX systems that we have and that currently bridge calls from various countries (FI, US, UK, NL, CZ, ES, JP, BR ...). But because our O365 account is originally based in a country where pstn calling isn't currently available (FI) we cannot (according to Microsoft support) onboard anyone else either. This means I cannot have any of our US based employees using cloud pbx as the underlying organisation doesn't support it. Bummer.
The end result is that we're currently using SFB for only internal meetings/presentations and internal voice, customer meetings/presentations with pstn conferencing added (works great) BUT having another SIP based legacy system on the side for outside voice and actively looking to replace the other system with something more modern and maintanable.
I did like the news that Salesforce and SFB would work together - it's awesome news. Even more awesome would be if it were for external things and not just internal chatting and talking.
As a fairly committed customer to SFB it's quite frustrating to have a feeling that Microsoft isn't all in on pstn calling in EMEA or at least looking at it extremely conservatively. It feels like you guys are looking at it locally per country instead of globally as an enabler for organisations with operations in multiple countries.
From a market point of view there seems currently to be a lot of competing products (definition: 100% cloud) in this market such as Zendesk Voice (it was called something else earlier), TalkDesk, etc. that can be used for both office and call center communications, RingCentral, etc.. Although most of them seem to outsource the heavy lifting to Twilio they're all aggressively trying to conquer the market in their niches.
Yes, I'm aware of "cloud connector". No, we're not interested in deploying the cloud connector VMs to mitigate this :)
FWIW I would like to get at least Finland for PSTN calling :)
