Good news, Netherlands and Ireland are now generally available for PSTN Calling from Microsoft on Skype for Business Online Cloud PBX.
PSTN calling is the service where Microsoft provide your user phone numbers directly from the cloud, acting as your “PSTN carrier”.
It looks like they are both still being managed through the service desk:
Germany and Belgium are still currently in preview. Here is the current complete list:

Tom, We’re seeing an increase in demand from S4B users for Twilio SIP trunk because we enable PSTN calling in over 70 countries. Including the availability of numbers in tricky places like India and China. We would love to run the proposition past you!
Could we arrange a time to speak next week?
Ciao
If it’s “PSTN Calling” i.e. user phone numbers are you using some kind of plugin?