@trillzoe60have you updated the phone's firmware? Was it working before? Retrace your steps. What was the last thing you did before it stopped working?
@eastcoastbelleis this an unlocked phone? Did you get it from Samsung? If so, you could go thru boost website activate the phone & it will tell you if it's compatible & @ the same time get the sim card from them. Here's the link https://activate.boostmobile.com/bring-your-phone?intnav=TopNav:Phones:BringYourPhone Hope this helps!