The path /usr/local/bin/composer is not in your PATH, executables in that folder won’t be found.
Delete the folder /usr/local/bin/composer, then run
$ mv composer.phar /usr/local/bin/composer
This moves composer.phar into /usr/local/bin/ and renames it into composer (which is still an executable, not a folder).
Then just use it like:
$ composer ...