Q: my phone says no sim. how do i fix it?

Try the following steps:

TS2802 iPhone: Hardware troubleshooting

"No SIM installed" alert (GSM models only)

1. Remove the SIM card.
2. Verify that the SIM card is not damaged or dirty, then reinstall the SIM card.
3. Try turning iPhone off and then on again.
4. Wait approximately two minutes, then see if iPhone detects the SIM card and if it will register on the network.
5. If that doesn't work, try another SIM card for that carrier, if possible, to see if it is detected.
6. If the message still exists, please go to: apple.com/support/iphone/service/faq/ for information on service.

Note: If you need to send your iPhone in for service or if you want to temporarily use a different phone, you may be able to use the SIM card inside your iPhone with another GSM phone.