My (least) favorite variant of this is the telemarketers who wait for you to say "hello", then, after they quickly conference in the actual operator, they say,

My (least) favorite variant of this is the telemarketers who wait for you to say "hello", then, after they quickly conference in the actual operator, they say, "Oh! Sorry, I was having a problem with my headset. Anyway, I'd like to ask you about..."