FedEx-Shipping phone number in the lable

functions.php

add_filter('wf_fedex_request','my_call_back', 10, 2 );
    function my_call_back($request,$order){	
		$phone = !empty($order->shipping_phone) ? $order->shipping_phone : $order->billing_phone;
		$request['RequestedShipment']['Recipient']['Contact']['PhoneNumber'] = $phone;
        return $request;
    }