If "less than a second later" (after your whistle) the horn sounded, there is no timing error due to lag time. Now you've got to decide which whistle was first. If it was your partner's, the call is held ball, game over. If you go with your foul and Team B is in the bonus, then we have bonus or double bonus. As I read it, Team A is up two, if it's bonus or double bonus and the first throw is missed (the lane is clear), game over, don't shoot the second if in double. If no bonus, obviously game over.
Now, what'd I miss....I'm sure I missed something!