Your data resets every calendar month. Or you could try and use all of it up in some sort of weird data usage challenge. You can't roll data from one month over to the next.

You can also choose to renew your plan early if you run out of data, or upgrade your plan before it resets.

You can choose to top up your data by purchasing add-ons in the Plan section. This data will be valid for 30 days, so they will carry on into your next month’s plan.