Next time he phones, tell him you know who he is, and you're imagining parting his pert little buttcheeks right at this minute. Then make some soft moaning sounds for a few minutes. Odds are they'll never phone again.
Alternatively, kick the **** out of the likely suspects until you find out who it is, then break their fingers. They'll usually not phone again.
Alternatively, kick the **** out of the likely suspects until you find out who it is, then break their fingers. They'll usually not phone again.





