Are you sure? I admit without knowing what the other half is it's hard to say, but the only call-like features I can see are on that gray colored one. There's a hint of a dome to his head, but the rest don't show any phenotypical hallmarks.
Did the person who sold you the ducks say they were 100% purebred calls, or something? You said in your OP that they were "supposed to be". I mean if it's not important to you, that's awesome, they're still a buncha cuties! But if you only bought them BECAUSE they were calls, and you wanted to either breed them or sell them, I'm afraid you were misinformed. :/ Where did you get hem from?