Folks;

I live and work in Bucks County, PA (Central Bucks).  I use several
AT&T Wireless phones for personal and business usage; currently I have
a TDMA service and a dual-band GSM / TDMA service (with the Siemens
S46).

It's time to upgrade the TDMA service.  I've tried most mobile
providers over the years -- Verizon will not work at my home so it is
not an option (and I know it's not GSM).  This leaves AT&T, T-Mobile,
and Cingular.

My AT&T GSM service is acceptable, but I have to use TDMA as I go
north in Bucks County (Quakertown, etc.) and the single in my house is
weak.  I think I want to get a 850 GSM service for better building
penetration and coverage, but Cingular as the lock on this in service
for my and a number of surrounding counties.

But when I had Cingular 16 months ago, they kept F'ing up my voicemail
and once shut off my service for a past due payment when I hadn't even
received the bill (and no payment was yet due).

So my questions are: If I use AT&T's GSM service and get a 850 capable
phone, will it use the Cingular towers in my area?  Or should I get an
unlocked GSM phone to help with tower / provider selection?  Anyone
out there in my area want to tell me why they like Cingular so much
better than AT&T?  How about anyone that lives in [semi] rural areas
... did getting a GSM 850 service help with coverage or building
penatration, or am I worrying about nothing?

I'm interested in hearing from others who've conquered similar issues.

Thanx in advance ... Phil