LG MM-535 Owner's Manual page 136

Caller ID allows people to identify a caller before answering the
phone by displaying the number of the incoming call. If you do not
want your number displayed when you make a call, just follow these
easy steps.
Press
*
Enter the number you want to call.
Press
To permanently block your number, call Sprint Customer Service.
When you're on a call, Call Waiting alerts you of incoming calls by
sounding two beeps. Your phone's screen informs you that another
call is coming in and displays the caller's phone number (if it is
available and you are in digital mode).
Press
second call.)
Press
.
.
. (This puts the first caller on hold and answers the
again.