If you wish to change the language of the display texts, then you must also change the system language on the handset. A different language can be set for every handset on the system. 

Press the Talk key. 

Call the system menu. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the language you require. 

Press the On-hook key to end the process.