Selling a block/charge no-call

[La Rikardo]

Under a minute left in a boys JV game, A has blown a double-digit lead in the second half and now trails by three. A1 makes a steal and goes on the fast break. B1 obtains LGP in front of the basket before A1 goes in for the layup. A1 moves to avoid B1, but still makes some contact and B1 falls hard and awkwardly to the floor. I decided not to call a foul and I'm confident in my decision. If I had called a foul it would've been PC on A1 -- B1 was certainly not guilty of a foul in my mind and A1 made an effort to avoid contact.

A's coach went crazy, yelling that I can't no-call here, that he just wanted a call one way or the other. With as hard as B1 hit the floor, I imagine that my lack of a whistle could come across as indecision. As some of you may know, my background is as a soccer referee, and when we make a big no-call we sometimes give a big NO! signal with the arms to let everyone know that we saw the contact and decided not to call a foul. Obviously this doesn't work so well in basketball, so does anyone have any tips to help sell a no-call in a situation like this?