I'm operating with an Alctel A392A. The problem I was experiencing was that
after trying to send a call or after receiving one, the phone would stop sounds
(both at the remote location or on my phone). After receiving the manual, I
noted that item 10 (on p. 6 of the manual) is a volume control. When the phone
is in Call mode, pressing this key (which is on the left side of the keypad half
when the phone is held as shown on p. 5 of the manual) it will Mute the remote
end of the call. That seems likely to cause the symptoms identified above.
Solution: Hold the phone so your fingers are touching the phone exactly on
the ends of the hinge. If your fingers slip down to the keypad level, you may
inadvertently squeeze what is the "mute" button during a call. That seems
likely to cause a loss of connection with the symptoms described above.
In other words, avoid squeezing the lower half of the phone on the left side
when you're making or receiving a call.
I've tested this approach on several incoming and outgoing calls. So far this
suggestion has worked.