I wanted to send the items within a listbox.One item at a time

this is the code snippet:

For i = 0 To 5
SMSPort.Write("AT+CMGS=" & Chr(34) & sender & Chr(34) & vbCrLf)
SMSPort.Write(listfiles.Items(i).ToString() & vbCr & Chr(26))
System.Threading.Thread.Sleep(800)
Next

And I tried this:
SMSPort.Write("AT+CMGS=" & Chr(34) & sender & Chr(34) & vbCrLf)
SMSPort.Write(Textbox1.text & vbCr & Chr(26))
System.Threading.Thread.Sleep(800)

Both listbox and textbox don't allow me to send sms.

There's no error but there are no outputs also. I cannot send any txt messages. However I tried this to test my code.

For i = 0 To 5
SMSPort.Write("AT+CMGS=" & Chr(34) & sender & Chr(34) & vbCrLf)
SMSPort.Write(i+1 & vbCr & Chr(26))
System.Threading.Thread.Sleep(800)
Next


And so I received 5 text messages with outputs: 1 to 5.


For i = 0 To 5
SMSPort.Write("AT+CMGS=" & Chr(34) & sender & Chr(34) & vbCrLf)
SMSPort.Write("arra" & vbCr & Chr(26))
System.Threading.Thread.Sleep(800)
Next

I received 5 SMS with "arra".


Kindly help me with my problem. I can't figure out what's wrong with my code.