My iphone 4 got stolen? What should I do?

Two days ago my iphone 4 was snatched from my bag at Target. I didn't realize it was missing until several hours later. This is the first time this has happened, I always take good care of my cell and have never lost it. My phone is under my aunt's family plan so I called her and she got my cell's service terminated. People have been telling me recently that I can track my phone, or try to get it using the security footage at Target. My aunt has been doing a lot for my family, and has given me the cell and paid for the service since I'm currently unemployed. I really don't want to cause her any trouble, I'm willing to downgrade to a cheaper cell. What should I do? What would be the wisest thing to do?

Start with calling the police and trying to see if they can find your phone

You can go on www.icloud.com and track your iPhone there. Or if you have another apple device you can locate it using that.

Call the service provider to track it.