Any Mobile Theme Switcher

Fatal error: Uncaught Error: Call to undefined function settings_fields() in C:\xampp\htdocs\krustpilsbaznica.lv\public_html\wp-content\plugins\any-mobile-theme-switcher\includes\amts-header.php:8 Stack trace: #0 {main} thrown in C:\xampp\htdocs\krustpilsbaznica.lv\public_html\wp-content\plugins\any-mobile-theme-switcher\includes\amts-header.php on line 8