Terminated from work because HR said I did not pass my drug test, fired on the spot. Went back to the clinic and was told my urine sample was inconclusive because temperature didn't register. Later I was told by HR I was fired because I declined to take a second sample. Which is false because I was not offered a second test. I have a document from the drug clinic manager stating that the statement of me refusing to take a second sample is untrue. I have been trying to talk to HR of the company with descriptive and informative emails, and they are just brushing me of with one or two line emails. I have been contacting HR and the company that does the background checks but have been getting little or no progress. What should be my next step?