Thank you for a prompt answer. Good to know; I am from Russia, and there it is a common thing to have a book of comments/notes in a cafeteria, hotel, restaurant, dorm etc. where anyone using the services of that place is free to leave any feedback, whether positive or negative, and any new visitors can just go through those notes and know first hand what this place is all about. Not to mention, it is also a proof of the complaint being made. Ok, I guess I'll try the certified mail then, thank you!