title: Submitting "operator commands" (e.g. remaining cash SIM credits) via AT commands to GSM phone/modem
body: <p>I'm a bit stuck investigating the how-to's of sending operator commands (dont know the correct technical term) using my GSM modem, in order to get an "alert" type message response from my network operator. Response characteristics are of course operator+command specific, but I figure they're used in similar ways regardless of country/network op.</p>
  
  <p>For example, dialling *123# on my cellphone, in order to get a prompt text response telling me my credit balance left on my "Cash type" SIM. That's what I need to do, but through AT cmds (and not on my phone :)</p>
  
  <p>Currently I'm using a Huawei E1550 3G modem for my dev. All modem comm is done through the <a href="http://www.scampers.org/steve/sms/libraries.htm" rel="nofollow noreferrer">GSMCommLib</a> library, if relevant. Also C#/.NET 2.0. I guess I'm primarily after some keywords/hints that can aid in googl'ing, but anything helpful is really appreciated!</p>