Just to add some info:
The Sodaq arduino code sends a 14 Byte message (which can be expanded to a longer one, as explained. This 14 byte data is send eventually by the modem by executing the following command:
In this message the 14 byte are written as hexadecimal ASCII (081310B803F2004FAB38000A87A9) chars, two for each byte. To make this more complicated the message is Base64 encoded by the CDP in the JSON message send to the north app. You have to decode this.
More info on this please see the presentation on : https://github.com/floresboy/NBIoT
I hope this explains things a bit,