thats a real call. howard and friends are listening to the call and they obviously have their microphone set to overlap the call, so listeners can hear howards reaction.
For him to pretend to be a cop is an offense within itself. The joke would be on him if ANYONE decided to press charges for imitating a police officer. As soon as the prankster issued the telemarketer a command as an officer he was in violation. Funny but very irresponsible.