Why wordpress wp-config.php file automatically rewritten? -

I have developed a WordPress site, today it is made .. When the site was in test server, But if I fix my work for a while through FTP, then after a few minutes I saw an error in getting installed in the database connection. wp-config.php file overwrites old file

I have tried the following steps 1. Rename database information 2. wp-config Remove .php files but automatically created a test server config file. 3. Change the wp-load.php files but again it turns into default data.