FactoryOutletStore.com Theft! Returned item and never recieved the refund Internet

We ordered a PetSafe Stay and Play Wireless Fence from FactoryStoreOutlet.com.  We set the system up and it had inconsistent boundaries so we called to company about a return.  We could only do an exchange because it was past the 30 days, which was fine because we instead ordered the YardMax Inground Fence.  The person that helped me said that we would get charged for the new item and that we would recieve a refund once the defective product was recieved.  We sent the defective product back on March 26th, 2014 and the USPS tracking confirmed that the item was recieved on March 29th 2014 by the company.  We followed all the instructions given to us by FactoryOutletStore and included the exchange form in the box with the item.  We have now been charged $299.95 for the defective product that we returned and recieved confirmation from the USPS that is was delivered at the warehouse and $259.95 for the new item we got in exchange.  FactoryOutletStores has not given us refund for the returned product and after talking to multiple people, holding for insane amounts of time, and never getting a callback from a supervisor after she said she would call us back, they are telling us they cannot give us a refund unless we have the tracking number from the USPS reciept we got the day we shipped it. Since the item was confirmed by the USPS to have been delivered 7 weeks ago, we no longer have the tracking number.  So the company now has the item we returned and our money.  We have been charged $559.90 for a product that costs $259.95, we should have at least recieved the difference for the exchange even if it's not a full refund.  We have our credit card documents and the email documents from the orders and the exchange.  If this kind of thing happened between two people during a transaction and not a person and an internet company, this would be considered THEFT!!!  All we want is our money back for the exchange we made.