Does anyone have suggestions on how to deal with this problem without
shelling out $300+ to change carriers?

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The problem I've been experiencing for the past five weeks (after about 16
months of great service) is when in-coming to my phones going directly to
voice mail even if the called phone is turned on and in a high signal area.
This happens on both of my lines/phones.  The problem occurs roughly 10% of
the time.  The phones are two different types, Samsung x427 and LG L1400

There is no message on the phones that there was a missed call or voice mail
was left.  If I do call the voice mail server, there will be a message there
if one was left.

I have contacted technical support numerous times.  All but once they had me
power-cycle the phone, they would call it and the call would go through
correctly.  They would say, "see, now it's working just fine".  The problem
is intermittent I explain to deaf ears.

On one call to tech support the person said they noted an error in the voice
mail routing setup, she changed it, and said proudly, "I'm 100% sure it will
be OK now".  Still not fixed.

I made a visit to a Cingluar store to complain.  They changed the simm card
and said try that.  Still not fixed.

Yesterday I had occasion to call one of my phones and 5 successive attempts
in about a 10 minute period resulted in immediate routing to voice mail.  On
four occasions I just hung up on one occasion I did leave a message.

The phone I called had no notification of missed calls or voice mail.  I
called voice mail and sure enough the message was there.  Oh, by the way
there was another voice mail from earlier in the day that we received with
no indication of the phone.

I went to the Cingular web site to check my account activity and noted in
the calling phone records the five calls noted above were there.  In the
called phone records there was no entry for any of the five calls being
received.

I have a neighbor with Cingular service, two lines, and he claims no
problems during this period of time.

I've talked with a billing department "supervisor" and asked if they could
compensate me in anyway for the sub-par service.  Her reply was, "we don't
guarantee all calls will be connected".  Cost to cancel contract, $135/line.

I got the number for the Cingular "area manager" (Central Florida ~ 50 miles
north of Orlando) from the local Cingular store and will try to contact her
on Tuesday.

Any suggestions are appreciated.  It's costing me money.  I drove 65 miles,
one way, last week to find out a doctors appointment had been cancelled.  Of
course the doctors office left a voice mail message that I never received.