title: How to delete all messages using AT commands
body: <p>I have a Huawei Modem connected to my VB.net project
  all AT Commands work such as <code>CONNECT</code>, <code>READ</code> and <code>SEND SMS</code></p>
  
  <p>The only thing that I cannot work with is the <code>DELETE SMS</code></p>
  
  <p>I have this code:</p>
  
  <pre><code>With SerialPort1
      .Write("AT")
      Threading.Thread.Sleep(1000)
      .Write("AT+CMGF=1")
      Threading.Thread.Sleep(1000)
      .Write("AT+CPMS=""SM""" &amp; vbCrLf)
      Threading.Thread.Sleep(1000)
      .Write("AT+CMGD=1,4")
      Threading.Thread.Sleep(1000)
      MsgBox(at_status.ToString)            
  End With
  </code></pre>
  
  <p>But the <code>at_status</code> throws me "ERROR" always.<br>
  <code>AT+CMGD=1,4</code> as what I've read on the documentation is the right command but it throws me an "ERROR" always.</p>
  
  <p>What do you think is wrong with my code? All other command works, except this.</p>