I have a contract with client as a freelancer.
Now I want to work with client as agency to have ability to involve some other guys as agency subcontractors to help me.
Can I sent contract proposal/invitation to my client as an agency?
You're a Non-Exclusive member of your agency, which means that you can choose whether you want to start a contract with a client under your agency or your individual freelancer profile. You may check this help article to learn more and how to go about doing that.
Thank you for your message. While applying to jobs from your agency account, you will have an option to select your agency and the agency member you would want to send the proposal from. You can refer to this Help page for more information.