Please be aware that if you have bought a router or Mifi device directly from a mobile network operator, then there is a possibility that the device could be locked to their network.
There are a few things you can do to check:
1. If you have one available to you, then put a SIM card from a different network operator in the device and see if it picks up a signal, if it does then the device is not locked and if it doesn’t then it is likely locked.
2. If the mobile network operator logo is printed directly onto the device then it's likely that it is locked to that network.
3. You can contact the network you purchased from directly and ask them if the device is locked, you will need the device serial number to hand.
4. Often network operators will be able to unlock the device for you on request, sometimes for free and sometimes for a small charge.