We are in the business of insurance restoration. We have a client that owes us, per our contract, almost $21,000. He has paid us the total of the original claim amount, but we negotiated with the insurance company on a much larger settlement to cover all of the damages. He won't pay the rest, stating that "we shouldn't know the total from insurance - it's not our business". We have his written permission to negotiate directly with insurance for the settlement, so of course we know the amount. What do we do?

We are in the business of insurance restoration. We have a client that owes us, per our contract, almost $21,000. He has paid us the total of the original claim amount, but we negotiated with the insurance company on a much larger settlement to cover all of the damages. He won't pay the rest, stating that "we shouldn't know the total from insurance - it's not our business". We have his written permission to negotiate directly with insurance for the settlement, so of course we know the amount. What do we do?