If you do a Wireless plan change or activated a new cellular phone that is mid billing period, your usage is pro rated from the date of your activation or change to the end of your billing period. Any overages that occur will be billed at regular rates.
For example: if your plan includes 100 minutes and your billing period is from the 1st to the 30th of the month and the change to our account occurred on the 15th you will have 50 minutes free in your plan because you are paying from the 15th to the 30th. (100 mins / 30 days x 15 days = 50 mins)
It should be noted that your recurring fee is also prorated, so you will be charged a "partial" monthly service fee (MSF) as well.