SharePoint online webservice authorization question

I want to Get list collections of SharePoint online, by using web service, while it returns 401 forbidden.

My code is 

var req = (HttpWebRequest)WebRequest.CreateHttp("https://***.sharepoint.com/_vti_bin/Lists.asmx");
req.Headers["SOAPAction"] = "http://schemas.microsoft.com/sharepoint/soap/GetListCollection";
req.ContentType = "text/xml;charset=utf-8";
req.Credentials = new NetworkCredential("***@***.onmicrosoft.com", "SptTest12#$");
req.Accept = "text/xml";
req.Headers["X-FORMS_BASED_AUTH_ACCEPTED"] = "f";
req.Method = "POST";

And Set the httpwebrequest body

string GetListCollectionsSOAPTemplate =
                    @"<?xml version='1.0' encoding='utf-8'?><soap:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'><soap:Body><GetListCollection xmlns='http://schemas.microsoft.com/sharepoint/soap/'></GetListCollection></soap:Body></soap:Envelope>";

However it returns 401 forbidden.

BTW,

I can login in the browser successfully.

Thanks for any help.