diberry - 10:26 pm on Sep 24, 2013 (gmt 0)
graeme_p is right. It sounds like this person has been clever enough NOT to send a fake DCMA (which is how I routinely deal with *actual* content theft). I also agree that the effort they've made kind of speaks for itself as to damages.
The trick will not be in PROVING there has been damage - the voicemail is defamation and you could sue for something like intentional infliction of emotional distress just for that. But you want to be able to give the judge some reasonable-sounding estimates, based on some kind of followable logic, that backs up the number you're asking for. Your attorney should be able to advise on this. If he says you can only ask for actual, provable specific amounts of money, that's just not correct.
Side note: I've worked in some very litigious fields and dealt with a lot of lawyers. Not only do they all have slightly different approaches, but some of them just plain don't know what they're talking about or have no ethics to speak of. Make sure what this lawyer is telling you sounds reasonable, and if s/he seems too mousy or too aggressive, don't hesitate to have some free consults with a few others and get a feel for who you trust.