Flow Chevrolet Flow Auto Plaza A simple battery exchange Internet

I had a so called new battery installed on 02/05/2011 due to battery losing charge when car sat for a few days not weeks. Took car to dealer and had replaced but the same problem persisted and I was unable to get back to dealer so I did my own research. 

Took battery to Advance auto for testing out of the car which battery failed the voltage test need replacing.
Had to jump car before I was able to drive which made me think they never changed battery but charged for one. 

I called before visiting dealer when I had a moment from my work schedule talked to a person in the department who told me to bring battery and they would do a pro-rated charge.
Being free on the 24th of December 2012  I took battery in for a replacement and was informed I had to bring the car in the other person working didnt know the procedure for replacement under warranty. 

Needless to say either they are telling me I am not competent enough to know when a battery is bad or their technicians are not worthy of checking batteries in vehicles.
 
I installed a used battery from Wal-Mart with lower cold cranking amps that my Chevy van uses and let the car sit for a week intentionally just to see if it would crank and believe it or not the car cranked with no problem and it has lower cold crankin amps than the dealership battery.

I bumped up the wait time to two weeks and the car still started with no problem. Now ask yourself how can a used  battery out perform a new one which was barely used? Can I trust dealerships anymore or should I do the work my self which I would be more secure and happy with.  Why couldnt they just warranty the battery and get me a new one obviously it is not the car thats the problem.