You have to pay for the plan dude. You can't do that behind your mom's back.
A cheap plan will cost you $400 a year, and the bill gets mailed home.

I'm trying to buy a phone behind my mom's back, and I was wondering, when you buy the phone, do you have to do anything else? like Fill out a form, give them a credit/debit card number, or just get it? Don't you have to tell them what plan you want, such as Prepaid or Monthly? btw it's Virgin mobile I'm trying to get.