How can I set the number+extension which is shown to called people

I’m trying to show my extension-number to callees, but either that is not supported by my provider, or I just don’t get it right in the configuration of the extension.

When I call someone (outbound) from any extension, the callee just sees xxxxx-0 instead of xxxxx-abc (where abc is the extension-number.)

System is a asterisk 2.4.x (latest) with an up-to-date freepbx installation.

I am using a digium-card (Wildcard TE120P) for outbound connections.

Thanks for your help.

Many telco’s and providers, if not all, only allow outgoing caller-id’s which match the phonenumber (or a DID phonenumber) of the trunk concerned. Also, some use a fixed caller-id per trunk.