Nikon

I purchased a new nikon d300 camera from tristate they shipped the camera to me when it arrived the lens was defective. I called and was given an rma to send the camera back meanwhile they shipped me a replacement. They charged my credit card again for the replacement and told me that when the original arrived back they would issue a credit to my card for the charge. They got the camera back on oct 6 and to this date they have still not issued the credit. I have called them numerous times. Spoken with several people in the customer service department and been told lie after lie. Promised a refund, promised to send copy of the credit via fax, etc. To this day still no credit. Meanwhile they just keep giving me the run around on the phone. I have now placed a complaint with the credit card company and am still waiting for the paperwork to arrive to challenge the charge on my card account. Tristate has now had the camera back for 30 days and has still not issued a credit which is in clear violation of the credit card agreement. Help me get my money back please>