i have some problem with web request

Dim postData As String = "u=%C4%B1%C2%B0%C4%B1&t=1385069699&b=SYMBIAN_KEYPAD&ma=3&signature=c103511ba5e93d665cb023a7522dffa0&mi=3"
       Dim tempcookies As New CookieContainer
       Dim encoding As New UTF8Encoding
       Dim byteData As Byte() = encoding.GetBytes(postData)
       Dim postreq As HttpWebRequest = DirectCast(HttpWebRequest.Create("http://shop.nimbuzz.com/index.php?"), HttpWebRequest)
       postreq.Method = "GET"
       ' postreq.KeepAlive = True
       postreq.CookieContainer = tempcookies
       '  postreq.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; ru; rv:1.9.2.3) Gecko/20100401 Firefox/4.0 (.NET CLR 3.5.30729"
       postreq.ContentType = "application/x-www-form-urlencoded"
       postreq.Referer = "http://shop.nimbuzz.com/index.php"
       Dim postresponse As HttpWebResponse
       postresponse = DirectCast(postreq.GetResponse, HttpWebResponse)
       tempcookies.Add(postresponse.Cookies)
       'logincookie = tempcookies
       Dim postreqreader As New IO.StreamReader(postresponse.GetResponseStream())
       Dim thepage As String = postreqreader.ReadToEnd
       MsgBox(thepage)