Let me start by saying I'm being vicious, and have no interest in adding myself or prison staff to such an abrasive caller.  However, if the caller were to call the prison: no person answers, but an automated system does with a list of instructions: "for medical press___. For Industries, press ___" etc.  The library isn't an option, but maybe the idea of having reached the prison would scare your caller...?
I used to work for a call center where callers called in from all over the country.  Those too cheap to call 900 #'s called our 800 lines asking for specific "customer service representatives" (those of us with mezzo soprano and alto voices).  I remember one man in Louisiana got arrested.  He called back not very happy, but it put an end to nefarious calls....
Jackie @ the Maine State Prison