LVNV Funding LLC Convergent Attempting to collect a non-existing debt Renton, Washington

Yesterday, I recieved a letter of collections from Convergent Outsourcing Inc., LVNV Funding LLC. According to their letter, they are seeking to collect a debt on behalf of Citibank. This raised a red flag in my head, because previously, I had printed out my credit report and paid on all listed outstanding debts. Nowhere on my credit report was there any Citibank account, outstanding or otherwise. I re-printed out my credit report from Experian, once as I suspected, no listing of any Citibank debt. I then called up Citibank directly to see if there was any records of any accounts held in my name and social. None were found in their records. I am sending them a letter to each of the three addresses listed on the letter they sent me (which is another red flag in my mind, that they would have three different mailing addresses), and I am sending them all as certified mail. Should they try and hit me on my credit report afterwards, I have already spoken in my letter that I will bring them to court for a lawsuit, which would be my first ever, and hopefully last. I don't generally like the idea of suing, but in this case it would be justified.

The three mailing addresses listed on this debt letter are: ATERSO01 PO Box 1022 Wixom MI 48393-1022

Convergent Outsourcing, Inc. 10750 Hammerly Blvd # 200 Houston, TX 77043

Convergent Outsourcing, Inc. PO Box 9004 Renton, WA 98057-9004 (This one is the one I'm supposed to send money to)

The debt they are claiming I owe is 1,171.72, but they say on that same letter that they are willing to settle for 410.10