any advice would be appreciated

Purchased a cell phone from Wireless Experts 12/07, and after a long wait, received an EMPTY box. After nearly four hours of trying to reach Wireless Experts by phone I was told by Mike at Wireless Experts (four hours later!!!) to file a claim with FedEx and complete an RMA form and fax it to Wireless experts. I did both promptly. FedEx returned to my home and collected the empty box the next day. After weeks of ABSOLUTELY NO COMMUNICATION from Wireless Experts, I began to email and call again to check my claim status. My emails were answered with "you need to call us", and my attempts to contact by phone were useless. I then called FedEx to check the claim status, and was told that a claim check had indeed been issued several days before to Wireless Experts for the full amount requested. I then informed Wireless Experts of such via both email and phone call (I was lucky enough to have someone answer this time), and requested a refund, as I was not interested in reordering. Wireless Experts had now been paid twice for the same item. No refund was ever issued, so I canceled the payment through my credit card, resulting in a reversal of the charge through PayPal. NINE MONTHS LATER, I receive a letter in the mail informing me that Wireless Experts has sent me to a collection agency for failing to pay for an item that I not only never received, but that they were already reimbursed for. In the nine months prior to getting the collections notice I did not once receive any type of communication from Wireless Experts informing me that they believed I owed them money. Wireless Experts is engaging in deliberate shady activity by waiting nine months to initiate a collections process, when they know that most individuals will no longer have access to information such as tracking and claims numbers. I should have been wise enough to review Wireless Experts on the BBB site, as I would have found out that the receive a rating of F. The collection agency has now told me the burden of proof is entirely on me. They say that Wireless Experts was not paid by FedEx, and that they are not required to have any further contact with FedEx. It seems to me they should be sending FedEx to collections, not me. FedEx has told me it keeps computerized records for only 90 days, so my chances of proof are gone. Since it has been nearly nine months since the incident with Wireless Experts, I have deleted any emails that may have contained tracking information. My numerous attempts at contacting Wireless Experts since receiving the collections letter have all ended the same as nine months ago.... they do not answer their phone! A recording comes on the line and says they are away from their desks or with another customer and then requests that you send them an email instead. My attempts at email are responded to with "please call us". The folks at Visa were also unable to reach Wireless Experts, and closed their investigation in my favor due to lack of response from Wireless Experts. When I explain to the collection agency that FedEx can not provide the only proof I need, they deem me uncooperative (yes, I did use an angry tone), and call me a liar. So, bottom line, Wireless Experts sent me to collections for a phone I never received, the cost of which was reimbursed by FedEx, and for which a replacement was not sent. How can I owe Wireless Experts for merchandise I NEVER RECEIVED?????
Should I try harder to get FedEx to track down the information about the claim check they issued Wireless Experts? It is my word against Wireless Experts, and I am sure the collection agency isn't going to side with me. I am confused and angry, and any advice would be appreciated.