They never bother to leave any kind of a message, so now they're blocked. At my house, no message means you didn't actually want to talk with anyone. Do it again and you're blocked.
Posts for some of their other numbers indicate they may be calling on behalf of Credit One Bank. They're bottom-feeders, so it would be absolutely no surprise if Credit One Bank is using them, since they're bottom-feeders, too.
you can block that number from your cell if you get something called call control,its free and ive been using it for a couple of months,you will see where they called but the blocker rejects there call,you can add up to like 8-to10 numbers to the black list if you need to ,hope this helps