The blank user calls can thus be a 'pin code' call accepted on the extension number shown on the TNG report. The cost thus belongs to the extension number and not the pin code.
Suggestion:
- Please check that users are not allowed to dial out without using a pin code.
- If you have pin code users and user without pin codes (not allowed to dial out, only receive calls), then management needs to be done to prevent user from asking pin users to make calls on their behalf and then transfer it.