In "Pizza Delivery," Squidward is answering orders from a fish who is ordering a pizza.
In "Big Pink Loser," Patrick takes the position of the phone-answerer at the Krusty Krab in attempt to get a trophy, only for him to think the callers are asking if he's a Krusty Krab when they're really asking about the restaurant.
In "Graveyard Shift," the phone rings a few times, but there is no one there.
This object is the subject of the "No, this is Patrick!" meme.