Ajax Call not Working in Plugin

You need to add the ajax callback action on your plugin file or themes functions.php like as below:

add_action( 'wp_ajax_fetch_data', 'fetch_data_callback' );
add_action( 'wp_ajax_nopriv_fetch_data', 'fetch_data_callback' );

then you need to put all the featch_data.php code inside the callback function ‘fetch_data_callback’ like as below:

function fetch_data_callback(){
//your function code goes here
wp_die() // need to add end of the function
}

In Jquery

 var action = 'fetch_data';

 $.ajax({
        url:"<?php echo admin_url( 'admin-ajax.php' ) ?>",
        method:"POST",
        data:{action:action, minimum_price:minimum_price, maximum_price:maximum_price, modoconf:modoconf, modoserv:modoserv, sub1:sub1, sub2:sub2},
        success:function(data){
            $('.filter_data').html(data);
        }
    });