Woah! If you made another individual account within the past 30 days you may be able to return the phone and not be charged for the service and then just add a line. I don't know for sure if you can do this but AT&T may be able to put it into a family plan. Dial 611 on your AT&T phone and talk to customer service.
*Please do your part and come back to choose best answer. Thank you.