Please note that to be a duplicate the following fields must have the same values:
DATE-TIME
EXT
NUMBER
LINE
DURATION
For explanation of possible duplicate calls see the following links:
- Ericsson
Conference calls and Call forwarding OR Duplicate
Ericsson: Duplicate calls on same extension - Asterisk
TNG Asterisk and speeddials - Found on Panasonic but can also be for other PABX units:
Duplicated calls in Topaz