Are you sure you are using the correct method names, the method signatures do not match;
In Course you have;
public static bool Updateuserdetails(string Name, string useremail, string usercont)
In the WebService you have;
Db_Helper.Course.Updateuserdetails();
and
Db_Helper.Course.Saveuserdetails(Name, useremail, usercont);
Should the second call in the webservice not be
Updateuserdetails(blah blah blah)
; and bin the first one.