Are Freelance Designers Covered Under This Act? How Can I Get Paid?

I have been doing freelance work for a company. I have a full-time job, and I do freelance graphic design work on the side. I signed a new contract with a design company in October, 2019 to do work on an hourly basis, as needed. In their contract, it says this for payment. "FEE. For services to be rendered under this Agreement, Contractor shall be entitled to a fee according to the fee schedule set forth on Exhibit "A" which is attached hereto and made a part hereof. Said fee schedule may be amended from time to time by KSA&D sending notice of such amendment to Contractor at the address of Contractor set forth in Section 12 below and Contractor agrees to accept such amendment unless Contractor notifies KSA&D in writing within three (3) days after receipt of such amendment. All such amendments shall be effective immediately upon receipt unless otherwise noted by KSA&D or objected to by Contractor. Said fees shall be payable in monthly installments for services rendered in the prior month. Contractor shall submit invoices for all fees due under this Agreement." I started work the first week of November and sent an invoice in December. I then did more work in December and sent another invoice in January. I have not received any form of payment thus far and they keep saying they will send it, but they never do. It is now February, and they have not paid me for November yet. I haven't received one cent. My outstanding invoices for them total $1575.00 What can I do? Can I charge interest? How much? If I have to go to court, will I most likely win? I kept all correspondence from them and there have been no issues mentioned, so I know that my work is fine. I followed up repeatedly to make sure they had everything from me, and to get their input. They are just screwing me around with payment.