Why recently can't make outgoing calls through Companyflex sip trunk?

[Issue Description]

The Companyflex sip trunk was working fine on your PBX, but recently when you make outgoing calls through the SIP trunk, then received '403 Forbidden' from the SIP provider. 


[Applicable Models]

Yeastar S-series PBX



SIP provider did some changes on their side probably after 2022, June.

1. They request the INVITE 'Contact' header should be the SIP trunk Username,

2. They request the INVITE should include 'P Asserted Identity' with the SIP trunk DOD number. 



1. Please upgrade the S-series PBX firmware.

a. For S-series V2, please upgrade to, then download pbxcenter-s_series-1.17.9-0.20.tar and upload it to the PBX App Center->Upload page

b. For S-series V4, please upgrade to, then download pbxcenter-s_series_v4-65.1.10-0.4.tar and upload it to the PBX App Center->Upload page


2. Set the sip trunk number as the DOD number, the DOD number format should be '+(Country Code)(Area Code)(Number)'. Then set the SIP trunk 'Outbound Parameters->P Asserted Identity' with DOD Number. 




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  • 0

    Hi Gary,

    thanks for the workaround given above. But I have one more thing:

    When I am trying to upload and install the pbxcenter-s_series_v4-65.1.10-0.4.tar  to our customers s50 v2 with firmware running it says " please upgrade firmware to version" which should only be compatible to v4 of the appliance, as you wrote above, and the installation of the pbxcenter was not successful.

    What could we do?

    Greetings and thanks in advance


    Thanks for your support.

  • 0

    Hi Stefan,

    I am sorry that I made a mistake. S50v2 should download pbxcenter-s_series-1.17.9-0.20.tar , I changed the link. You can download and check it. Thanks again for your notice. 

  • 0


    thank you very much! Outgoing calls are possible again.




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