I had the same thing happen to me.
We bought a pair. When we got them home and looked closer, we started to question more. The guy that sold them to us was so sure and talked so highly of the kinds, etc. So, we had no doubt they were what he said.
I brought this up with them and they actually agreed to take them back. But, as like you... they were already in the tank, etc.
So... I just kept them. Hope they end up a descent looking fish as they were $40 for the pair.