Do you mean changing password with Roundcube webmail? If so, you can disable this in its password plugin config file: roundcubemail/plugins/password/config.inc.php.

Please just take a look at this file, at least open it and read several lines.

This is my current configuration,  so there is already false. but it not working...

$rcmail_config['password_driver'] = "sql";

// Determine whether current password is required to change password.
// Default: false.
$rcmail_config['password_confirm_current'] = true;

// Require the new password to be a certain length.
// set to blank to allow passwords of any length
$rcmail_config['password_minimum_length'] = 4;

// Require the new password to contain a letter and punctuation character
// Change to false to remove this check.
$rcmail_config['password_require_nonalpha'] = false;

// Enables logging of password changes into logs/password
$rcmail_config['password_log'] = true;