No sim? Says searching? What do I do?

Everytime when I turn on my iPhone, it'll say either "searching…" or "no sim" at the top. I've tried resrting my phone, taking out the sim card and puting it back in, turning on made and turning it off. Help me please?! I don't know what to do, and I need to be able to get in touch with people.

Are you trying to use a SIM card from another provider?

If so you need to unlock the phone.

If not, contact your service provider.