We were notified by a factoring company that a subcontractor had factored an invoice we owed the subcontractor. The payment terms were with in our payment policy period. The subcontractor took the funds from the factoring company and did not pay his suppliers or his subcontractors. We are now getting demand letters for the factoring company to pay the invoice however we are not paying them but using the mobey to pay the outstanding invoices the subcontractor owes. Do I have to pay the factoring company or offest the payments from what the subs owes?