If it was a commission based job, it is likely that you signed a contract setting forth the rate or percentage of compensation and the terms and conditions of the contract. I would have an attorney review the contract.
The information provided in this answer does not create an attorney-client relationship. If you are interested in his legal services, feel free to call Chris at (303) 409-7635 at his law office in the Denver Tech Center. All initial consultations are free of charge.