A few weeks ago I had an Alert on my credit report saying that I had XXXX new collection accounts from National Credit Systems. After reaching out to the company they informed me that they mailed a letter 5 times to a known bad address. When asking them why I was not alerted they said they tried but they had XXXX pieces of returned mail. So, with further concern I hired a private investigator XXXX XXXX XXXX XXXX to find out that they were advised to send it to the office of XXXX XXXX XXXX. XXXX XXXX XXXX had the proper address to forward any and all correspondences. I have emails to substantiate this claim. I also have proof that I was sued and paid the bill in full! They are trying to collect a debt that is no longer valid.