string URI = "https://hhhh.domain/sms/url_send.html?originator=55555&";
[DataMember]
public string destination { get; set; }
[DataMember]
public string content { get; set; }
string userPass = "password=fffff&username=bbbbbb";

public void sendParameters()
{
        WebClient wc = new WebClient();
        NameValueCollection myCollection = new NameValueCollection();
        myCollection.Add("destination=", destination);
        myCollection.Add("&content=", content+ userPass);

        byte[] responsebytes = wc.UploadValues(URI, "GET", myCollection);
        string responsebody = Encoding.UTF8.GetString(responsebytes);

}

{"An exception occurred during a WebClient request."}