Most likely the towing company's position about what you owe is correct in that it placed the notice in the United States mail addressed to you twice where you received the second notice advsing you of the car's impoundment.Under the mail box rule, if mail is placed in the United States' mail correctly addressed to the recipient with postage pre-paid, it is presumed that the mail is received by its recipeint if it is never returned to the person sending it.Unfortunately the towing company has the upper hand against you. It has your vehicle and you probably want it back. Getting it back comes with a price that is higher than what it should be had you received the first mailing of its impoundment.Good luck.