...unless they screech "stalker!" and swing a warrant for your arrest, for having the temerity to write to their home address. Some of those stalking laws are crazy.
Though, back before caller ID was common, I used to get hammered by calls from the local newspaper, five or six times a day, trying to get me to subscribe. I worked nights, so they kept waking me up; I had to leave the ringer turned on, because my elderly father might need me. No amount of "don't call this number again" ever worked. I finally found the home number for the publisher, and called him at 3 in the morning and explained I resented his employees calling me half a dozen times a day. He hung up on me. The next night, nobody answered. The third night, he had an answering machine. His idiots still kept calling, but I got some small measure of revenge, anyway...