Prefill the billing fields in woocommerce checkout

Solution:

Use following code

<?php
/**
 * Pre-populate Woocommerce checkout fields
 */
add_filter('woocommerce_checkout_get_value', function($input, $key ) {
    global $current_user;
    switch ($key) :
        case 'billing_first_name':
        case 'shipping_first_name':
            return $current_user->first_name;
        break;

        case 'billing_last_name':
        case 'shipping_last_name':
            return $current_user->last_name;
        break;
        case 'billing_email':
            return $current_user->user_email;
        break;
        case 'billing_phone':
            return $current_user->phone;
        break;
    endswitch;
}, 10, 2);