This is usually siteurl and/or home in the database, wp_options table if you want to go search for this. but a quick fix is to define these variables in the wp-config file. Connect with FTP, edit the wp-config.php file and add the following two lines after updating example.com to your domain:
define('WP_HOME','http://example.com');
define('WP_SITEURL','http://example.com');