Try:
string Url = @"http://203.122.58.168:8000/servlet/com.aclwireless.enterprise.prepaidcbs.listeners.GetCredits?userid=kuldeep&pwd=hisarama";
string result;
HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(Url);
myRequest.Method = "GET";
using (WebResponse myResponse = myRequest.GetResponse())
{
using (StreamReader sr = new StreamReader(myResponse.GetResponseStream(), System.Text.Encoding.UTF8))
{
result = sr.ReadToEnd();
sr.Close();
myResponse.Close();
}
}