We have all had fatalities. It is part of the hobby, an unfortunate part.
After 4 days, if the fish dies, it is most likely due to conditions in the tank. But even with the benefit of the doubt, and the tank is pristine, expecting to be refunded the money after 4 days is pushing it.
Could have been the fish was cyanide caught, could have been overstressed in the car ride, could have been the over acclimation-4 hrs is a bit much-what method of acclimation did you use by the way? You wrote: "it was properly acclimated (4 hours) and no light for a day...so i made sure that everything was done correctly,...even placed a heater in with the fish while acclimating to make sure that the temp was the same when he entered his new home." Were you acclimating in a bucket with the drip method?
The fish could have been stressed in the tank by other inhabitants, the chemistry difference could have been too much, way too many factors, and again, 4 days later points in a direction I can't blame ont he store.
I think getting your credit card company to refund was basically stealing.
If you have spent that much $ in the past ($1500?) then they must have been doing something right. Granted, I would have had you bring in your tank water for testing and then made a decision, but it is generally understood in this hobby that you look for healthy fish at the store, and that is where the store's responsibility ends.