Sending commands with NB-IoT SIM not working

Rob A
Rob A
in IoT

I am trying to follow this document: using a registered and active SIM purchased from Twilio, but always receive back a response:

Free Msg: Unable to send message - Message Blocking is active.

Using the AT command set, I am able to open a https connection, as well as ping an IP address, so the device is successfully connected to the network. How do I send commands to the 2936 shortcode (tried both "2936" and "+2936")?



  • Hi, Rob. Can you check that Messaging is enabled in your Narrowband SIM’s Rate Plan? Meantime, I'll see what else the cause of this might be.

  • Yes, it looks like it is enabled in the rate plan:

    I had also opened a support inquiry and they are saying that SMS is not supported on NB-IoT, but I can find no documentation to that effect and it seems like that would be the only way to use the Commands SMS feature. SMS is also mentioned on the main NB-IoT page ( in the Breakout SDK section so it seems unlikely that SMS wouldn't be supported.

  • From talking to the support folks, I can confirm that the Narrowband SIM doesn’t support messaging. Sorry about that, and that the page you refer to may have led you to think otherwise — it should have been updated. I'll get it changed. The tutorial you mentioned earlier is for the Programmable Wireless SIM, but I’ll update it to clarify that it’s not intended for the Narrowband SIM.

  • That's really unfortunate. I thought the whole purpose of the Narrowband technology was for very small messages, but it appears that I will have to build this talking to Twilio's REST interface with all of the overhead of DNS lookups, TLS negotiation, HTTP headers, etc. - that will burn through a lot more data than a SMS message would. I don't see any way to run Twilio functions via MQTT, so that is out.

    Thanks anyway for the information.