[amusedofficial]

You're not obligated to call a double foul unless and until you both signal conflicting calls, i.e. one signals charge and one signals block.

If you both whistle it, and even if you both go up with the foul sign, you still have the right to defer to your partner. You are not obligated to do so and may signal what you think you believe you probably saw, in which case it is a double foul. However, in the absence of conflicting mechanics, and where you have deferred to your partner, there is no double foul.

Perhaps I should say it's not a blarge until we say it is.