Assuming there is no legal question as to whether the customer owes the money, you may have to sue him in Wisconsin. If on the other hand he had enough nexus to PA, you could sue him at home in Philadelphia. What kind of business did you have? How is it that he came to owe so much?
Sue in Wisc. Need an attorney to accomplish your objectives. Who would write you a $44,000 check based on your letter, no matter how well crafted?
I am not your attorney. Contact an attorney for advice immediately.