http://www.ftc.gov/os/statutes/fdcpa/fdcpact.htm

(a) COMMUNICATION WITH THE CONSUMER GENERALLY. Without the prior consent of the consumer given directly to the debt collector or the express permission of a court of competent jurisdiction, a debt collector may not communicate with a consumer in connection with the collection of any debt --

(1) at any unusual time or place or a time or place known or which should be known to be inconvenient to the consumer. In the absence of knowledge of circumstances to the contrary, a debt collector shall assume that the convenient time for communicating with a consumer is after 8 o'clock antimeridian and before 9 o'clock postmeridian, local time at the consumer's location;

(2) if the debt collector knows the consumer is represented by an attorney with respect to such debt and has knowledge of, or can readily ascertain, such attorney's name and address, unless the attorney fails to respond within a reasonable period of time to a communication from the debt collector or unless the attorney consents to direct communication with the consumer; or

(3) at the consumer's place of employment if the debt collector knows or has reason to know that the consumer's employer prohibits the consumer from receiving such communication.