Your unused data is yours to keep in your data bank for as long as you stay on your current plan or change to a bigger one. Every month, all of your unused monthly or add-on data is added to your data bank.
If you're on one of our current plans ($15, $25, $30, $35 and $45 plan) - you can bank up to 300GB.
If you haven't switched over to one of our current plans, you can bank up to 200GB.
Please note that if you change your plan to a smaller one, your data bank will reset, and you will lose any of the data you had banked so far. From that point on, you can start banking any unused data again.