From Main Menu, go to SETTINGS > SYSTEM > HOME SCREEN SHORTCUTS.  Use the navigation keys to modify the appropriate navigation keys.

If you need any further assistance with this question, please contact the Sonim Customer Experience Center at 1-833-MY-SONIM (1-833-697-6646) or email us at [email protected]  We are open 24 hours a day, Monday-Friday and we will further assist in troubleshooting.