If you cannot negotiate a settlement with this person then your option is to sue them in small claims court. Here is the site for Wisconsin small claims court: http://www.wicourts.gov/about/pubs/circuit/smallclaimsguide.htm
You would sue this person for breach of contract and they would have to show that the cost or their services was the amount that they were paid. If not, you would recover the balance. You can also recover the costs of filing in small claims court. I hope that I have provided you with options.
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