What does pro rata mean?

It just means that the charge for your plan in the first month will be adjusted and charged from the time you activate your SIM card (if you got a new number) or from the time your number was successfully transferred to Circles.Life till the end of that month*.

For example:

If your monthly plan is $25/mth and you activate your SIM card in the middle of the month, you only have half a month to use your plan: the pro-rata charge will be $12.50!

*Please note that your first month's bill also includes your Pay-As-You-Go expenses for the month, any Add-ons (prorated) and your second month's plan charged in advance. For more details about your first bill, head here.