When enabling Caller ID Number on one of your DIDs, please be sure to configure your PBX to pass this DID as the Caller Number in your outbound calls.
By default, your UniTel SIP services do not set a Caller ID number for outbound calls through a SIP Trunk. This is by design to ensure that customers can set the "Callers Number" as needed for their specific routing purposes.
If your outbound calls are showing Unknown please check your PBX settings to ensure they are passing the desired Caller ID Number.