I know a director at the IRS and she received a letter from the state telling her she did her state taxes wrong (as did I). We both wrote polite and detailed letters explaining our calculations (actually I was owed $10 more that I originally calculated:) and the matter was dropped.

I suspect your letter fell into the hands of a part time clerk who then filed it in the circular "out" bin.

If you are in the right, I would call every day, document all the names of the people you talk to and try to talk to the head of the property taxing department, at least get their name. I would then send the letter every week and require a signature so you know who got the letter when they say they never got it.

If you bug them enough and talk to the right person you should be able to get this cleared up quickly. I would only get a lawyer if you do owe the money. A lawyer will help you out by haggling over the amount.