Me and some friends used to prank call people all the time a few years ago; one time we called this phone number information place (what the hell do you call it in English? ) and asked for the number to the phone number information place. :rolleyes2
They just went: "ahem, this is just a prank, right?" and we went: "...yes!"

...in other words...

"ähum, det här är bara ett skämt, eller hur?"
"..ja!"