Yes, it does sound like they are sending you the corp billing invoices. Trying to figure out their compensation rate can be as daunting as finding a low rate! Some are flat rate and that's it, some include a formula based upon number of award nights being redeemed, and yet others include overall occupancy rate for the property.

As suggested, keep monitoring you CC account and dispute any charges. In the worst case they may be checking to see if you object to the invoices before posting the charge. If that's the case, I hope they get NAILED for fraud!