Crazy. Yesterday I visited my carrier/ISP's local shop to discuss changing my mobile data plan. Turns out that this month they have a 3 GB bonus for anyone who upgrades or takes out a new plan. So I upgraded from a plan that gave me 1.5 GB of data per month to one with 2.5 GB & is $5 per month cheaper. I still have 8 days remaining of the old contract, so they've transferred the old contract period to the new contract data plan.
This means that factoring in the 3 GB bonus, I have 8 days to use 5.5 GB of mobile data before the next 2.5 GB month commences.