robot.txt blocked pages but still alive

You should make sure to place the robots.txt file in the root of your web folder. FTP servers have many folders and if you place the robots.txt file in the wrong one it will not work.

Robots.txt helps to control how search engine robots access your website. It will not restrict your pages from appearing in internet browsers.

When you say your pages are appearing at two addresses are you referring to http://www.example.com and http://example.com both showing the same content? If that is the situation you should use htaccess to apply a 301 redirect so the content is only available from one source. A 301 redirect will redirect users from the other source and automatically send them to your one source.

Robots.txt does not stop you accessing a URL. It cannot block access if something requests that URL.

It is a file that compliant bots download from your site, and then use to make a note of URLs that they should not request.

Robots.txt doesn't actually "block" anything at all. It is merely a list of questions that should not be asked.