Hi @pennyjulian, which modem are you referring to? I mean NBN (with 4G back up), mobile broadband (dongle), 4G home wireless broadband or 5G home broadband? Is the other modem that you have is from Optus as well.
You can give it a shot. If it is not an Optus modem and if it is locked to the other providers network that it belongs to then it might not work. See how you go.
If you need further assistance then you can speak with our Technical Support team via the → messaging service to assist you further.
@pennyjulianIf it's not an Optus modem then it may not work as Optus implements checks to ensure that some of their data SIMs only work in Optus supplied modems.
Some modems may be locked to certain networks (VMO's) and if this is the case then unless the network is Optus it will not work, but most data modems are not locked.
Either way give it a go. If it does not work check the APN. If you do not know what an APN is search for 'Optus APN list' and have a read up and use the one you think is right for you.