Anniversary billing is the standard method of billing for all of our low-end plans with less than 2.5GB of data. While the term "anniversary" is usually associated with a yearly event, in this case, it's monthly. Make sure to check the relevant Critical Information Summary (CIS) for your plan to see what kind of monthly billing it has.
With anniversary billing, your billing cycle will start on the date that your service is connected, and it will run until the same day on the following month. So if you signed up on the 15th of June your billing cycle would run from the 15th of June to the 15th of July, and then to the 15th of August and so on. All the additional service on the same account will be kept on the same billing cycle as it is for the first service and customers will get a pro-rata charge on their account for all the additional services connected with Moose.
Please see the image below for a more visual explanation.