How to connect and configure a USB GSM modem in FREEPBX16 for calls?

Search for chan_dongle

But note that appears to be abandonware. Also note that networks are starting to retire GSM (2G) and 3G, although I believe there are compatible dongles that do 4G.

I would recommend using a SIP to mobile air interface gateway, instead.

I am interested in chan_dongle. downloaded freepbx on the website freepbx but now I can’t find how to install chan_dongle