Uniden Cordless Telephon Owner's Manual page 27

You must subscribe
through your local
telephone company
to receive Call
Waiting Service.
[ 26 ] B A S I C S
If you have Call Waiting service and a call waiting tone sounds while
you are on a call, press talk/flash (or flash on the base) to accept
the waiting call. There is a short pause, then you will hear the new
caller. To return to the original caller, press talk/flash or flash on
the base again.
The voice mail LED on the handset is designed to work with your
voice mail service provided by your local telephone company. The
LED flashes when you have new messages in your voice mail box.
You may need to occasionally reset the indicator if it remains On
after you've retrieved your messages. To reset the indicator, when
the phone is in the standby mode, press and hold find handset on
the base until the paging sound stops (about 5 seconds).