tax impound account abuse?

[Mark Hu]

Our lender is impounding money for our property tax bill on our new condo. I've been checking up on them, and was recently astounded when they told us they would not be paying our supplemental tax bill (the difference between the old tax bill and new one based on purchase price of the condo). They have the money already in the impound account!
Isn't this extremely unethical? We would like to cancel this tax impound account immediately, but I've read it is very difficult. If they are being unethical can I take them to small claims court?