Inbound calls have no audio

Mine has a public IP address, and the ISP provided credentials that have no registration for both inbound and outbound calls. But when a call comes in, I see it but when picked both ends have no audio.
And when I do an outbound call, the extension instead calls itself. Is there any idea on this?

Did you mean ITSP?

Please provide the full log, with “pjsip set logger on” in effect. If not using SIP, please explain what protocol you are using. If using SIP but not chan_pjsip, please reconfigure for chan_pjsip (or, at least use the equivalent logging option on your legacy driver).