You can call into NPSTN from the PSTN by dialing +1 (406) 957-1122. You can then dial one of the phone numbers in the member list!
Want a number? Click on the button at the top of the screen that says 'Join NPSTN' or call +1 (406) 957-1122 (or any other PSTN Gateway Number) and dial 116 for the business office.
Due to server issues currently some gateways are down. (530) 537-0261 is a known good gateway. This will be fixed in a few days