> For the complete documentation index, see [llms.txt](https://kb.hostednetwork.com.au/support/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kb.hostednetwork.com.au/support/services/voice-over-ip-voip/general/3cx-guides/changes-to-default-3cx-headers.md).

# Changes to default 3CX Headers

In order for the 3CX PBX to function correctly with outbound calls when using the Hosted Network PAYG or Unlimited SIP Trunks you need to modify the default outbound parameters on the trunk.

If you experience issues with calls being rejected by the VoIPNow server or getting service unavailable messages please modify the below settings in the Outbound Parameters of the trunk:

| SIP Field           | Variable                                |
| ------------------- | --------------------------------------- |
| Contact : User Part | "AuthID" Authentication                 |
| From : User Part    | "AuthID" Authentication                 |
| From : Host Part    | "GWHostPort" gateway/provider host/port |

Changing the above settings should then allow calls to flow through the platform successfully.

If you still encounter issues with the calls please contact our support team via email at <support@hostednetwork.com.au> or via phone at 1300-781-148


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