Q: Have just upgraded to ios 7 on my iphone 4s. No SIM

Hey there nadsbug,

Thank you for using Apple Support Communities.

It sounds like even after restarting and reseating your SIM card, you are getting a message saying No SIM.

I recommend the steps from this article that you have not tried yet named:

iPhone: Troubleshooting No SIM

http://support.apple.com/kb/TS4148

1. Update your iPhone to the latest version of iOS.
2. Toggle Airplane mode On and Off.
3. Try turning iPhone off and then on again.
4. Check for a carrier settings update. Tap Settings > General > About. If an update is available, a prompt will appear.
5. Remove the SIM Card and verify that it is a valid, carrier-manufactured SIM. Also verify that it is not damaged, worn, or modified. Then reinsert it.
6. Restore the iPhone.

If you still are unable to resolve this issue, contact Apple support for further assistance.

All the very best,

Sterling