Serious bummer. Unless your pond gets overflow from a water source with fish, like a nearby stream, I'd be concerned that you stocked bullheads. I too would contact the fish farm. That just shouldn't happen.
The good thing about catfish is that they are really hardy, they grow really fast, and even edible size catfish are inexpensive to stock.
I expect that many others will post. But, if it were my pond, I'd kill the pond by draining it, liming it, or using rotenone. Then I'd find a reliable source of 10 to 20 inch channel cats. Maybe your dealer will work with you, and provide you with 50, or so, edible size channel cats. It doesn't take them long to start taking bait.
Good luck,
Ken
