Roger gets upset at Stan for quoting the Ghostbusters to him. However in season 4, episode 12 (Roy Rogers McFreely), Roger makes the same exact quote ("I ain't afraid of no ghosts") when referring to Hayley's body painting.
Stan tries to call 911 but the line has been cut. The phone would not have been able to have audible beeps if the phone line was cut since it also provides power to the phone.