Good Day.
I am registering my trunk through MTN and I’m getting one way voice. But through the other ISP it works perfectly fine.
How do I resolve this?
By asking MTN what you are doing wrong, or looking at the Asterisk logs, and other logging information to discover where the RTP, is getting lost, where is it actually going to, and what in the SDP, etc., is causing that.
Even if there is someone here who is familiar with MTN, you will need to provide them with details of your network topology and configuration. If they are not familiar, they will also need the logs of the SIP and SDP changes.
Did you mean ITSP, rather than ISP?
Which version of Asterisk are you using, and which SIP channel driver are you using?
Port has been forwarded and the SIP ALG has been turned off, Well by ISP I mean when I have connected with another Internet Provider it works and Calls we can hear each other but when I connect by MTN it fails to breakout
Is your internet service provider the same as your internet telephony service provider?
Especially if not, did they provide the router, and is there anything more complex than very basic NAT done by that router?