Harris County Toll Road Authority Texas Toll Roads rip you off. Houston, Texas

I sold my car in 2010, the person who purchased it rode with my tag for over a year and received numerous toll violation notices of which none came to me because I had moved to Florida and no longer lived in Texas. Recently I received letters from the toll road authority charging me the tolls in question with an additional administrative fee for each. At that time I immediately called them and explained that i had sold my car and have a bill of sale signed to prove it. There response was "sorry it's your tag and you are responsible". I proceeded to say that I would pay the toll portion of it, but for them to consider waiving the admin fee since it was way over $600 at the time.

Well....so much for customer service, just a few days ago, I received letter from an attorney regarding the tolls and now the fee went up to $1510.50. So from a dozen toll violations that cost at the max...$1.50, I now am being demanded to pay $1510.50. How is that a fair and valid amount especially under the circumstances that I explained. I understand that running a toll is a violation as it is a violation in the state of Florida too, but ripping a consumer off is a violation to me and should be illegal to steal from the consumer. It appears to me that these charges are obviously ridiculous, but also abusive and I cannot afford to pay this amount that I am being charged. I am disputing these charges and hope that HCTRA makes some adjustments to resolve this matter before I have to go and seek legal advise.