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Ha ha Robi, I did just that in America when some very rowdy students in the next room kept us up all night, so the next night when they were tired, I kept phoning their room (it was direct dial, not through the switchboard) and whenever they answered it, I hung up, I did that for several hours, biy it felt good, but I was really tired the next day. Alternatively, blow a whistle down the phone, dodgy unless you have caller id and you know it's not someone who should be calling you!