Problem with Online Broker

My online broker is voiding a sale I made of an option. Can you tell me what government agency I should contact to make a complaint?

I am a law school graduate. What I offer is mere information, not to be construed as forming an attorney client relationship.

You need to contact the SEC (securities and exchange commission). You will find the link below for your convenience:

He probably voided the option for a number of reasons. You need to make sure you didn't do anything wrong before you contact the SEC.
http://www.sec.gov/