Just out of curiosity, did they "approve" your invoices specifically and expressly (as to the amount of the debt) or did they just say something along the lines of "let us see them and we will discuss them"? If they approved them expressly was it done in writing or just verbally and who was it who approved the debt (did they have authority to bind deeproot)?

I hope you get paid what you are owed by whomever owes you the money. Good luck.