-phone rings late at night and is answered by person who is not a phone book wanker-
"...Who are you and why are you calling me?"
"eeehhrmm.... who ur you??"
"Not telling you!"
"well yer a wanker then!"
Both parties are aware who the real wanker
is, but only one is enough of a wanker
to actually state that the person receiving the call is a wanker
- the phone book wanker
- will then get bored and either do what wankers
do best or go back to his (probably sticky) phonebook to find another hapless victim.