Update - I bought myself a $2 pre-paid Telstra SIM - I’m connected!
I didn’t bother paying for any credit, so I can only receive, but I CAN receive! 
I’m connected via CAT-M1
PS: a fantastic plain English tutorial:
https://www.developershome.com/sms/howToUseHyperTerminal.asp
Understanding AT commands is hard - @Tim should write a tutorial 
