Continuity mistake: Near the beginning, Giovanni Ribisi has a voiceover in which he refers to the #6 (subway) going to Fulton Street. The #6 train does not stop at Fulton, the 4 and 5 do.
Continuity mistake: When Seth's father calls him asking if he can help out with Seth's stock deal, listen carefully to everything said. When the FBI agent plays it back, right before Seth's father leaves the FBI office, saying "You can't charge me with anything," the agent plays back the recording of him and Seth talking, and the placement of what they are saying is totally different from the actual conversation.
Continuity mistake: At the beginning of the movie when it shows Seth on the bus there is no one sitting in the seat in front of him. The scene cuts to inside the bus then pans forward to show two occupants in the seat in front of him snorting cocaine out of a briefcase.
Continuity mistake: In the final scene, Seth's Volvo is parked correctly in the parking spot next to a red Ferrari and a grey car. But when the wide shot reveals the FBI vehicles moving in, the Volvo is parked sideways and the grey car is gone. There is no way he would have time to park it like this, and make the other cars disappear.
Continuity mistake: In the scene where Seth goes into the office at night to get his briefcase/bag after he gets dropped off at his car, he sees the compliance officer shredding documents. The compliance officer's sleeves go from being buttoned at the wrist to being rolled up between shots. There is not enough time between the scenes for him to do this.
Answer: I spent some time as a telemarketer (my apologies to anyone I may have called) and only certain people got headsets. They were used as a reward for top closers. Everyone else had to use handsets in a room similar to the one in the movie.