Hi Wooi,
I don't think the problem lies with the CTI portion of the config :) If you are trying to call using the Message button on the IP Phones, I think this is missing;
Configure Voice Mail Profiles
Voice mail profiles provide an easy way to manage multiple voice mail systems. A voice mail profile is used when you press the Messages button on a phone. Also, you can avoid the need to manually configure the CFB and CFNA numbers when you forward calls to voice mail.
The voice mail pilot number is configured with the DN on the CTI route point that is configured for voice mail.
The Cisco CallManager Administration Guide explains in detail how to configure a voice mail profile. But, you generally only need to add a pilot number and then a voice mail profile, usually a name is selected that identifies the remote site, with the pilot number selected. The profile is then applied to individual phone DNs. This enables you to check the Voicemail selection for CFB, CFNA, or even Call Forward All (CFwdAll).
CallManager for Cisco Unity Express Configuration Example
http://www.cisco.com/en/US/products/sw/voicesw/ps5520/products_configuration_example09186a0080289ef0.shtml
Hope this helps!
Rob