First, try to resolve the problem by direct contact with vendor/client in polite manner, this is always the easier and faster way to resolve it!
Then have a look at BoonEx Terms Of Use, if you still sure that you need to raise a dispute then the procedure is described here:
http://www.boonex.com/trac/dolphin/wiki/GenFAQ#HowtosubmitaCopyrightInfringementcomplaint
