WCF / ASMX :: Can't Access Service.svc.cs

Im using VS 2008, 3.5 framework I want to use wcf, but javascript cant access to myservice.svc error : Message: 'MapService' is undefined;

calling mapservice ;
function getselectedIl() {
var firstLetter =
"caglar";
var proxy =
new MapService();
proxy.GetSuggestions(firstLetter);
defining mapservice;
<asp:ScriptManager ID="ScriptManager2" runat="server">
<Services>
<asp:ServiceReference Path="MapService.svc" />
</Services>
</asp:ScriptManager>
mapservice.svc.cs;
[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class MapService
{
[OperationContract]
public string GetSuggestions(string firstLetter)
{
return "basarili";
}
}