مشكلة باستخدام اللغة العربية باستخدام AT Commands

using System.Collections.Generic;
using System.Text;
using System.IO.Ports;
using System.Threading;
namespace ConsoleApplication1
{
class Program
{
static AutoResetEvent readNow = new AutoResetEvent(false);
static SerialPort port; static void Main(string[] args)
{
try
{
Console.Write("Enter the port name your phone is connected to: ");
string portname = Console.ReadLine();
port = EstablishConnection(portname);
string recievedData = ExecuteCommand("AT", 300);
recievedData = ExecuteCommand("AT+CMGF=1", 300);

char q='"';
String command = "AT+CUSD=1,"+q.ToString()+"*100#"+q.ToString()+",15";

recievedData = ExecuteCommand(command, 300);

if (recievedData.EndsWith("\r\nOK\r\n"))
recievedData = "Message sent successfully";
// recievedData is unkown encoding
}

}
catch (Exception e)
{
Console.WriteLine("Error Message: "+e.Message.Trim()+"\r\nHit any key to Exit");
Console.ReadLine();
}
finally
{
if (port != null)
{
port.Close();
port.DataReceived -= new SerialDataReceivedEventHandler(DataReceived);
port = null;
}
static string ExecuteCommand(string command,int timeout)
{
port.DiscardInBuffer();
port.DiscardOutBuffer();
readNow.Reset();
port.Write(command+"\r");
string recieved = receive(timeout);
return recieved;
}
static string receive(int timeout)
{
string buffer = string.Empty;
do
{
if (readNow.WaitOne(timeout, false))
{
string t = port.ReadExisting();
buffer += t;
}
}
while (!buffer.EndsWith("\r\nOK\r\n") && !buffer.EndsWith("\r\n> ") && !buffer.Contains("ERROR"));
return buffer;
}
static SerialPort EstablishConnection(string portName)
{
SerialPort port = new SerialPort();
port.PortName = portName;
port.BaudRate = 19200;
port.DataBits = 8;
port.StopBits = StopBits.One;
port.Parity = Parity.None;
port.ReadTimeout = 300;
port.WriteTimeout = 300;
port.Encoding = Encoding.GetEncoding("1256");
port.DataReceived += new SerialDataReceivedEventHandler(DataReceived);
port.Open();
port.DtrEnable = true;
port.RtsEnable = true;
return port;
}
static void DataReceived(object sender, SerialDataReceivedEventArgs e)
{
if (e.EventType == SerialData.Chars)
readNow.Set();
}
}
}

using System;