Ok just to reference your statement about data using seperate channels and what not I guess you are not privy to the technology used in cell towers, congestion is caused as a cell tower can only handle so many requests, DATA or VOICE.....
Fortunately, it doesn't work that way.
A common mistake is in thinking that an IP based backhaul means voice calls don't get dedicated resources. However, carriers use TDM and/or pseudo-wire circuits to make sure that voice calls get all the QoS they need.
Data has to share the remaining bandwidth and is what is subject to congestion.
So fyi Data requests can congest and cause problems with voice even on the Un Touched Super Squeeky Clean power known as Verizon's network.....
No. See above. Data loads alone should not cause problems with voice due to limited backhaul on either Verizon or AT&T. Data especially cannot cause a voice problem on Verizon because it's transmitted on separate channels.
Data can (and does) cause dropped voice calls on AT&T because GSM 3G shares the same channel for data and voice (thus allowing their simultaneous use). Data transmissions can affect voice calls, and vice versa. This is because more 3G voice or data users cause a cell's effective radius to shrink, and marginal users will often get dropped. So a new data user can drop voice users on AT&T.
Another problem with GSM 3G is that if you're on a voice call and then use data simultaneously, the phone+network has to drop the voice connection and reconnect instantly as a combined data call, which can fail. You might not even know the phone is trying to do this in the background for push email or notifications data. All you know is that your voice call dropped. (Which is why some people stick to EDGE, which does not support simultaneous comms.)
I get dropped calls constantly. I'd say it's approaching 50% of the time. I am not even in a rural area at all. My phone will say 3-4 bars and then when I go to make a call, it drops down to 0-1 bars. I just turned in on, just now and it showed 4 bars, and then it dropped to 2 bars immediately. I think their software is trying to be optimistic or something. It's like magic!
GSM uses a form of CDMA called WCDMA for 3G.
(W)CDMA works by having every phone talking at once, just like picking out a voice in a crowd in a noisy room. The more phones talking to a cell, the louder everyone has to talk to be heard. The overall signal level doesn't matter, but only the usable ratio of your own signal levels to the noise floor.
If a phone displayed this ratio, it would fluctuate wildly as users come and go. So idle phones usually display the steady power level of a transmitted pilot channel from the tower instead. Basically, the closer you are, the higher the level, which a user can understand.
Once you connect, the phone can actually determine the connection quality because then it knows its communication error rate. That's why the bars will fluctuate after connection.
Your phone could show only one bar of pilot signal, but still get a great connection if you're the only one using that cell. Or you could have full bars of pilot signal, but a terrible connection if you're sharing the cell with too many others.
So bars are basically meaningless until connected, and even then only show the quality incoming to the phone, not how well you transmit to the tower.
How would you go about finding out if a phone or carrier service worked in a certain area if you didn't consult other people or credible sources? Wouldn't you have to make a decision based on 'Other Peoples Opinions' in order to find out? If you know Verizon service yields 0 bars in your area do you know this as a previous Verizon service customer, consult someone directly or take the 'Opinion' of the AT&T salesman? 
