Very strange! You should only need to change the microSIM to change carriers. The RF is the same for all iPads. In Australia you can buy pre-paid SIMs. That

Very strange! You should only need to change the microSIM to change carriers. The RF is the same for all iPads. In Australia you can buy pre-paid SIMs. That is, you get a chunk of data which you have a certain time to use. Some options are as long as 12 months. Different carriers have different plans but it is not hard to find a plan that suits your usage pattern. And you can switch the SIMs between devices in your family.