How to change site_url() value in localhost?

Dear Friends,
I download my CI 3 web site files from live to localhost. But after changing the base_url in application/config/config.php , when I try to
login it goes to live site. When I look on form action I can see the live server URL value instead of local. In code I can see using site_url().
Where I can change this value to work on localhost ? Please advise.

Thanks
Anes P A