Hi Wissam,
The only alternative is to use a Headset, then you can configure Auto Answer;
In Cisco Unified CME 4.0 and later versions you can configure lines on specific phones to automatically connect to incoming calls when the headset key is activated. The phone cannot be busy with an active call and the headset key must be engaged to automatically answer calls. Incoming calls are automatically answered one by one on the phone as long as the headset light remains lit. For each ephone, you can specify one or more lines for headset auto-answer.
After a phone is configured for headset auto-answer, the phone user must press the headset key to start auto-answer. The headset light is lit to indicate that auto-answer is active for the lines that are designated in the configuration. When the phone auto-answers a call, a zip tone is played to alert the phone user that a call is present. To stop auto-answer, the phone user presses the headset key again and the headset light goes out. At this time, the phone user can answer calls in a normal manner using the handset.
To enable headset auto-answer, perform the following steps.
SUMMARY STEPS
1. enable
2. configure terminal
3. ephone phone-tag
4. headset auto-answer line line-number
5. end
http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/admin/configuration/guide/cmeanswr.html#wp1010363
Hope this helps!
Rob
