Geeetech

First off... I can talk to the board just fine. I use the Arduino 1.6.5 serial monitor + cr/lf. Works great.
But I never get connected to the AT&T network. Light flashes at a < 1sec rate.

After Investigating it appears the IMEI number is unknown to AT&T. They sent me a note saying that they don't ...

If I issue the following command:
AT+CSTT?
I get
+CSTT:"CMNET","",""

I think I need to change it to an AT&T network: "broadband"

When I issue the following command I get an ERROR

AT+CSTT="broadband","",""

So my question is, why doesn't this command work? Is there something I need to do to ...