How to attach PDF to a fax message?

I am trying to attach a pdf to a fax that i am sending using code below

HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);

Stream rs = wr.GetRequestStream();

StreamReader sr = new StreamReader(filepath);

byte[] fileStream = ReadFully(sr.BaseStream);

rs.Write(fileStream, 0, fileStream.Length);

sr.Close();

public static byte[] ReadFully(Stream input)

{

byte[] buffer = new byte[20 * 1024];

using (MemoryStream ms = new MemoryStream())

{

if (input != null)

{

int read;

while ((read = input.Read(buffer, 0, buffer.Length)) > 0)

{

ms.Write(buffer, 0, read);

}

}

return ms.ToArray();

}

}

I get back the response that Fax was Queued, but when I receive fax it is only default cover page. This mean the binary data was not attached. What am I missing?