Ok so I heard back from Snap/2DG.

I can switch across to a new unlimited plan, take my own modem, no connection fee and no term.

The discount is only $6 from my current plan, but I do get unlimited data and calling. Also can get the $10 extra discount for my 2DG pay monthly account.

To be honest I would be happy to lock it in for 12 months if there was a free modem, as my current fritzbox has been acting up a little. It might be on it's last legs.