CUCM has no idea of whether a DN configured on a phone is a number you created which can only be dialed internally, or a DID. That, you'll need to sort out after using CAR/CDR
You can try the device -> GW reports, there are many more reports, depending on what you need, you might find one which is more useful for you.
HTH
java
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www.cisco.com/go/pdihelpdesk
HTH
java
if this helps, please rate