Excise duty query

Dear Sir/Madam My company is based in Kolkata,India.I was supplying steel CRC Sheet to a company in Ahmedabad named XYZ Pvt Ltd who is a manufacturer of steel drums/barrels. My payment got stucked with XYZ Pvt Ltd Company in the month of Oct 16.In order to pay my dues this XYZ Pvt Ltd Company based in Ahmedabad suggested me to supply her fresh steel sheet in order to manufacture drums/barrels on conversion basis and she will arrange selling of finish drums to her clients in Ahmedabad directly through my company.By doing so she will be able to pay my dues in 3-4 months.She also suggested me to take VAT Registration in Ahmedabad in order to facilitate this business routing. Since we do not have excise registration and since we are based in Kolkata, this XYZ private limited told us that they will issue our company’s commercial invoice and their cmpany’s excise invouice gate pass. All was going well as per plan in the month of Nov 16 and Dec 16.Suddenly my payment against sale of finished drums/barrels got stucked with one of her clients in the month of Jan 17 which we noticed when her client’s payment against our 4 commercial invoices stopped coming.When we talked to this XYZ Pvt Ltd Company she told that her client will make payment within 30.01.2017.But we didn’t received any payment on 30.01.2017.Then this XYZ Pvt Ltd Company stopped talking to us and also didn’t respond to our emails.Then we contacted this client of XYZ Pvt Ltd Company and came to know from this client that they had not received any drums against our above 4 commercial invoices but they had received drums against excise gate pass of XYZ Pvt Ltd on same date and same excise bill no.which XYZ Pvt Ltd Company has issued to us in support of our above 4 commercial invoices for extending benefit of excise duty to her client.In short this XYZ Pvt Ltd company was using and issuing our commercial invoice to her client by giving her excise invoice gate pass as supporting document for extending excise duty benefit to her client as myself is not registered in excise department.Thus we came to know that this XYZ Pvt Ltd Company has issued 4 false commercial invoices of our company and kept us waiting for 45 days for payment.Now this XYZ Pvt Ltd Company is not paying our due payment. Please suggest what legal step we can take against this XYZ Pvt Ltd company and her client. Regards Siddharth Gadia Email id-sudarshantrades@hotmail.com Mobile No.9830177733