To answer your last question, you can use www.optoutprescreen.com to get off the mailing lists (or more accurately to prevent the credit reporting agencies from supplying your info to the card issuers for "pre-approved" offers).

However, if you already have a citicard, it may not stop citi from sending you its own offers though (as the "do not call" list does not stop entities with which you have an existing relationship). I am sure there is an answer to that question but I don't know what it is.