I'm a subcontractor after I completed a job. The supervisor on the project ask me to come back to do more work. I informed him that I would have to bill him for additional work. He said ok just send invoice to his boss. When I sent the invoice to his boss he told me he did not approve the extra work and that all extra work had to be approved in writing by him beforehand. He said maybe the supervisor would pay me personally. I have been trying to reach out to him about this but no response.