SoapServerException when calling GetListItems

I am trying to call GetListItems in a specific calendar in sharepoint site. However everytime I try to call GetListItems I get an error saying:

Exception of type 'Microsoft.SharePoint.SoapServer.SoapServerException'

My calendar is in a sharepoint site whose URL is:

https://myteam.company.com/sites/TeamSite/Lists/Calendar

My url for my lists service is:

https://myteam.company.com/sites/TeamSite//_vti_bin/Lists.asmx

And I call getlistitems as follows:

appSettings = ConfigurationManager.AppSettings;
credentials = new NetworkCredential(appSettings["Username"], appSettings["Password"]);
var doclist = new Lists() { Credentials = credentials, CookieContainer = new CookieContainer() };
var xmlDoc = new XmlDocument();
XmlElement query = xmlDoc.CreateElement("Query");
XmlElement viewFields = xmlDoc.CreateElement("ViewFields");
XmlElement queryOptions = xmlDoc.CreateElement("QueryOptions");
queryOptions.InnerXml = "<ViewAttributes Scope='Recursive'/>";
XmlNode doc = doclist.GetListItems("Lists", string.Empty, query, viewFields, "0", queryOptions, null);

I always get an error when calling the getlistitems method. Is there anything wrong with my code? Thanks.