In Australia, none of the mobile carriers offer any unlimited usage accounts, those that do offer the larger usage accounts lock the account to the paired SIM Card # and IMIE modem number that they supply you with. Many people have attempted to negotiate with the carriers here in Australia to allow them to change over to a different IMIE, though to date the carriers simply will not do it.
In this case, we still would do something like what @kevin has mentioned using the USB into a Peplink router with an external mounted and frequency matched LTE MIMO antenna solution such as those found here in Australia from Telco Antennas
As a side note, we had to do this a lot until recently good quality LTE-A chip sets for commercial devices became available in Australia, now that the MAX range has the LTE-A chip sets, we have been a lot happier , here is @Alan’s previous post on these models.
If the carrier is locking the SIM to the IMIE, then you have to use that option from the carriers device, then how you get that connection going is open to lots of good options here.
Contact Peplink Support for your local certified specialist, the specialist will be able to help you make this work very well for you.
Happy to Help,
Marcus 