Motorola A780 Owner's Manual page 171

Problem
I tried to place
a call and
heard an
alternating
high/low tone.
I cannot
send/receive
calls.
My phone has
poor reception
and drops
calls.
Solution
Your call did not reach the wireless
system. You may have dialed the number
too soon after turning the phone on. Wait
until the display shows the name of your
service provider before making a call.
Make sure that you have a phone signal
(the signal strength indicator + should
have at least one segment showing).
Avoid electrical or radio interference, and
obstructions such as bridges, parking
garages, or tall buildings.
Your phone also may have the
call barring feature turned on. If you
know the call barring password, you can
change this setting in the security menu
(tap T Setup in the application launcher
screen, tap Security, then tap Call Barring).
Also, check to be sure your SIM card is
installed and working.
Make sure you have a phone signal (the
signal strength indicator + should have
at least one segment showing). Stay
clear of any obstructions such as
bridges, parking garages, or tall
buildings.
Troubleshooting 171