Complaining loudly rarely gets the desired results and I have dealt with many manufacturers about product failures, denied claims, other people who yelled at the warranty/service department people and all kinds of other situations. I have been incredibly PO'd at times but unless the person on the other end is unreasonable, I make a point of not yelling at them. First, they're usually just going by company policy and are trained to color inside of the lines. Second, They don't have the authority to do much, other than read from their book of solutions. In a case like this, it's best to remain calm and ask for a supervisor, telling them that the only reason you paid with the company card is that you just wanted to use that one instead of another. If it was for personal use, tell them this and explain that you don't need a receiver at your place of business.
From the Onkyo site, "#14. Products used continuously or for commercial applications. Onkyo products are intended for consumer use and are not designed for continuous or commercial use. In the event that the products concerned have been used commercially or continuously, the warranty period is limited to 90 days from the date of purchase."
They probably told you this but it doesn't help your case.
Is this receiver the kind that connects to a network? If it is, it may still show the IP address, which probably wouldn't match the ones at work.