As I am not licensed to practice in the state of Wisconsin, my answer is based on general legal principles. For a specific answer to your question you should consult a lawyer licensed to practice in your state. You may want to consult Jeff Biddle, an excellent lawyer in Gilbert.
A repo man can take your truck but he can't press charges and he can't charge you with a felony. In fact his threatening to do so is usually considered extortion. You might want to ask Jeff to consider writing the repo guy a sharply worded letter.