Just switched my number to a new iphone, but my old phone still works?

I just went and started an individual plan and got a new iphone 5, and they carried over my number from the virgin mobile prepaid i had before. My new iphone can make calls and send and receive texts… But so can my old phone. And when i called my cell number using my house phone, my old phone rang, but my new iphone didn't. Do i have to like cancel service or something? I'm confused about what to do, the guys at apple didn't mention anything about it.

Take the sim card out your old one and transfer it to your new one, and try telling your phone company, and cancel your old one.

If you can send and make calls from your iPhone, then you need to go back to where you got it or call your wireless provider and tell them that it is not linked up correctly.