NTTA North Texas Toll Authority Third notice of non payment Plano Texas

I have contact  them three times over the last 2 years for a vehicle I do not own anymore sold it in2010 for salvage. Theyb insist I am responsible since the tag resemble the tag of the vehicle I used to own. However looking at the blurry picture they send I can distinguish that it is not the same as the plate in question. Also with threat of misdameanor chargers or being unable to register the vehicle. Other that filing a law suite for harrassment  because obiviously they know when they look at  the pictures on their end they can see they contact the wrong person 1 the plate is different tha listed 2 the vehicle make is different than the one in question