Help expunging a three year old misdemeanor

[davidwang2006]

What is the name of your state? Texas

I made a stupid mistake almost 3 years ago -- forgot to take out a small kitchen chef knife from my carry-on luggage when trying to pass DFW airport security check. As a result they took the knife off, fined me $100 and let me go on the same flight the same day, without any arrest/prison. I took the flight to start working in west coast and never got back to Dallas.

Once in the new city I phoned them and told them my new address, that's why I got letter from Transportation Security Administration in Coppell, TX that says admin will accept $100 fine, in full resolution of the enforcement action. Thereafter I never got any letters/phones/emails from Dallas.

I thought it’s done as fine $100 was already paid in full and they sent me a letter (I still keep the letter) that says the fine (I just get the bank statement showing that amount on my check) would close the case with a full resolution. But to my big surprise, when I am preparing to take another new job these days, the background check from my future company discloses that they actually filed a misdemeanor (I guess it’s A class as the case number starts as MA***) on me and not closed yet. I guess the local misdemeanor court just sent the hearing letter to my Dallas address which unfortunately I couldn't receive. As I did not show up on the court date they issued a warrant.

How can I close the case / expunge the misdemeanor? Since it’s almost 3 years ago, is it too late to do now? Does paying the fine mean I am already convicted, therefore it can only be expunged, or sealed, or neither?