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.
For example customers may want to use different Phone Numbers for outbound calls that orignate from their Sales team as opposed to their Support Team. Or, if each Employee has their own DID number, you can configure your PBX to send that employees' DID for their outbound calls.