Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, bear with us; re-confirm and post back with the complete model number of the base unit.
And would a link to an electronic copy of the manual serve your need please?
The KX-TGA402 is the supplied handset for several base unit models such as a KX-TG4011. Its features and functions therefore would be dependent on the base unit model number it is linked to.
On the otherhand, a KX-TGA401 is an optional handset.
Still, please see the link below.
The manual for the base unit using the KX-TGA402 is in a Portable Document Format (PDF) file and can be viewed in most web browser. Click on the link to open the file or right click then select “Save As…” to download the file. It would require Adobe Acrobat Reader or equivalent for this purpose.
All the functions then of the KX-TGA402 would be included in the aforementioned User's Manual.
Were you able to download the manual?