Unfortunately, stores often misidentify, misname, or make up names for the fish they are selling because most people will never know the difference. The stores around me all have a "30 day guarantee" on the fish. This means that, essentially, they can misname a fish and give me the wrong advice on caring for it, and then when it dies from lack of proper care, I can take it back and get a replacement fish to kill the same way. Yahoo!
It's so important to do your research before going to the pet store, unless you find one that is trustworthy. In my experience, no one who works at a chain pet store really knows what he/she is doing. I've listened to workers BRAG about how great they are and how much they love fish and then recommend that I put HUGE fish in a TINY tank (not to mention with other fish that it would eat in a minute, but he didn't bother to ask me what other fish I had in that tank). It's appalling.
Most cories are pretty easy, but there are a couple that have some more specific needs. And as a group there are a couple of specific needs (they need to be in groups, they are scaleless and intolerant of salt and meds, general pH reqs, etc).
My recommendation is to do some research and ask some questions on here before you make more fish purchases so you don't have to trust the people at the store, who you now know are not actually terribly helpful or educated on the "products" they are selling.