If you are not inclined to legal action, or if the client will not agree to the increased fees suggested by Scott, you might want to look into prioritizing this particular type of search. Paying clients get the top priority, and you will get to the problem client's search if and when you have time or the next time you have someone abstracting in that location. Gives the problem client the option of reassigning the search to an abstractor that does not mind working for nothing if the client does not like the availability of timing you have.