For a few weeks now we have been facing troubles when we try to make outgoing calls from our GSM device which is connected to a trunk with our FreePBX server.
We have reviewed the configurations of both the trunks and the VoxStack and no changes have been made since 2018.... However, it was until recently that outbound calls stopped working.
When we call from any softphone, the line appears as "user busy" and hangs up. In the logs of the device the error code SIP/2.0 603 Declined appears and from Asterisk it appears "Got SIP response 603 Declined back from".