Why's my SIM card not working?

So I've just got my first ever phone, and it's an iPhone 5s. I put the sim in and set the phone up, turned it on, and it said it had no service. If I go into Settings - Phone - Number it says unknown. How do I get it to work?

Added (1). So I've just got my first ever phone, and it's an iPhone 5s. I put the sim card (Vodafone) in and set the phone up, turned it on, and it said it had no service. If I go into Settings - Phone - Number it says unknown. How do I get it to work?

Sometimes it can take a few hours to register with the phone. Try turning it off and on again, sometimes that triggers it to connect.

Sounds like you have a bad SIM card.

Check with your carrier about it.

Make sure the SIM is valid-check with the carrier that issued it. And make sure the phone is not locked to a different carrier.