Mac .... take it back and exchange it. And when you do, check the new batteries for a sticker or code that tells you when the battery was made & pick thru them until you find one that's the youngest. If all they did was "charge it", and didn't do a load test ... I'd suggest they do one if they have any problem taking it back in exchange for a new one. If it's the battery, and for all accounts it sure sounds like it is, then a load test should reveal the problem.
You might also send a PM to Catfan ... he's our resident battery guru, and he'd give you the straight & skinny on the situation. I'd do that before taking my advice on what to do. (he might tell you the same thing, or he might have a different opinion but I defer to his advice over mine)