You will need to modify the template assigned to that particular phone. Depending on the service you are using (CallManager onsite or hosted VoIP, or other options), you may or may not actually have access to make these changes. See also Cisco's guide located at http://www.ciscosystems.am/en/US/docs/voice_ip_comm/cuipph/7960g_7940g/7_0/sip/english/administration/guide/7960usrS.pdf
Answers & Comments
You will need to modify the template assigned to that particular phone. Depending on the service you are using (CallManager onsite or hosted VoIP, or other options), you may or may not actually have access to make these changes. See also Cisco's guide located at http://www.ciscosystems.am/en/US/docs/voice_ip_comm/cuipph/7960g_7940g/7_0/sip/english/administration/guide/7960usrS.pdf