I cannot dial a 1300 number from a Telstra TMS Sim. I get the phone message "The phone number you dialled is not in service"
Telstra TMS Sim supports 1300 dialling.
If you get a "Phone not in service" message when calling a known working 1300 number, check if a + is automatically added when you dial on the Iridium handset.
To remove the +, navigate through the phone menu Setup> Number Entry and select Do Not Prefix.
Each time you dial now, phone number will not be prefixed with a +.
This should allow you to successfully call a 1300 number.