By default, Delacon will pass through the caller ID of the original caller through to the termination point to be displayed on the operator's phone screen. However, your requirement may not be to know the caller's phone number (which will always be available in the call reports), but instead that the call is coming through the Delacon provided number before it is answered. The Show DNIS feature can be used to show the static DNIS number instead of the callers phone number. This static number could be subsequently saved as a contact on the customer side so Delacon calls are always identified.
The DNIS number will either be the Delacon number that the caller dialled or in the case of some numbers types (for example; Australian 1300 numbers), will be a dedicated local number.