Hello - We've completed work on an extensive remodel of a commercial bar / restaurant. The work has been installed and the restaurant has been opened. We are a subcontractor of the GC. We have submitted invoices for our last progress payment as well as our retention payment. The GC has not acknowledged receipt of either invoicing package, and isn't responding to snail mail, e-mail, or phone call inquiries as to status. We submitted these invoices approximately 30 days ago. We've asked if there is punchlist work requiring attention, but have heard nothing from the GC, their project manager, or their accounting department. What is our best course of action to receive payment at this point?