It's for You Tales from the Cryptkeeper : Season 3 Episode 11

For Christmas, Gary recieves a phone line for his bedroom with the proviso that he doesn't ""abuse the privilege."" Naturally, Gary immediately begins making prank calls, but he soon finds the tables turned when one of the people he called begins stalking him via telephone. Gary pays the caller a visit and discovers Mrs. Emma Needham, an old lady who soon proves that she's not as nice she initially appeared...