send extension number

I would like to send my extension number as well, how can I set this up?

When I call out, the extension number is not displayed. Only my main number is displayed. SIP provider says that it is not transmitted.

Why you want to send the internal extension number in a outbound call?

so that customers know who called them

As far as I know, only the Outbound CID Number is shown during an incoming call. You can assign a specific Outbound CID Number to each of your Agents if you want!