Uncaught SoapFault exception: [soap:Server] System.Web.Services.Protocols.SoapException: Server was unable to process request

I am new to SOA

$wsdl = 'http://ift.tt/10DtFmU'; $options = array("exceptions"=> 1, 'soap_version'=>SOAP_1_1, 'trace'=> 1'); try { $client = new SoapClient($wsdl, $options); $client->WSValidate('username', 'password'); } catch (SoapFault $E) { echo "Exception Error!\n"; echo $E->faultstring; }

ERROR:

Exception Error! Function ("WSValidate") is not a valid method for this service

if i am going to use any other method then it gives me folllowing error

Fatal error: Uncaught SoapFault exception: [soap:Server] System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.NullReferenceException: Object reference not set to an instance of an object. at BusBookingAPI.WSValidate(AuthenticationData credential, String strUserHostAddress) in c:\inetpub\wwwroot\api.tektravel.com\BusBookingAPI\App_Code\BusBookingAPI.cs:line 733 at BusBookingAPI.GetAllCities() in c:\inetpub\wwwroot\api.tektravel.com\BusBookingAPI\App_Code\BusBookingAPI.cs:line 77

please help me to sort out this problem. I dont know how to use the services using soap.