This feature is available only for Android and iOS Jabber, not for Windows etc.
First create a Mobility Profile, Call Routing -> Mobility -> Mobility Profile.
This is a global setting.
Go to end user and assign mobility for the user needed
Then go to device configuration and make sure for the following
- Assign a softkey template that has Mobility key assigned on "On Hook" and "Connected", Create on if needed.
- Assign the English United States on User Locale (Required as stated)
- Assign an Owner ID and Mobility user ID
- Assign a CSS that allows you to reach the mobile number on "Rerouting Calling Search Space"
- On "Transfer to Mobile Network" select "Use Mobility softkey (user Receives Call)"
- On "Dial via Office" select Enable
- On "Associated Mobility Identity" create a new mobility as follows
Apply configuration and logoff - login from mobile jabber and test.
Cisco reference
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/jabber/11_6/cjab_b_feature-configuration-for-cisco-jabber/cjab_b_feature-configuration-for-cisco-jabber_chapter_0100.html#CJAB_TK_S6472988_00