Core Issue
This is Working As Designed (WAD).
Resolution
For an IP phone to be able to initiate a full-consult transfer, it has to have more than one line available. For example, you need to configure and assign an ephone-dn [number] dual-line. This allows the IP phone to have two lines or channels associated with the one directory number.
Configure dual-line DNs to overcome this problem.
Ephone-dn : A software construct that represents a line that connects a voice channel to a phone instrument where a user can receive and make calls. An ephone-dn represents a virtual voice port in the Cisco CallManager Express system, so the maximum number of ephone-dns in a Cisco CallManager Express system is the maximum number of simultaneous call connections that can occur. This concept is different than the maximum number of physical lines in a traditional Telephony system and also is different than the maximum number of telephone or extension numbers that can be assigned.
This example output shows how to add the huntstop channel command in the ephone-dn configuration:
CMECUE(config)#ephone-dn 1
CMECUE(config-ephone-dn)#huntstop channel
channel Stop hunting on 2nd channel of a dual-line dn
Refer to these documents for more information: Defining Network Parameters and Call Transfer
