iphone 5s can't receive signal,and my SIM card wasn't broken

Hello there.

The following Knowledge Base article offers up some great recommendations for troubleshooting the issue you're describing:

iPhone: Troubleshooting No Service

http://support.apple.com/kb/ts4429

If you encounter any of the above symptoms on your iPhone, follow these steps to try to resolve the issue. Test after each step.

1. Toggle airplane mode: Tap Settings > Enable Airplane Mode, wait five seconds, then turn off airplane mode.
2. Turn your iPhone off, then on again.
3. Remove the SIM card and verify that it's a valid, carrier-manufactured SIM. Also verify that it isn't damaged, worn, or modified. Then reinsert it.
4. Check for a carrier-settings update. Connect to a Wi-Fi network. Then tap Settings > General > About. If an update is available, iOS will ask you if you want to install it. If Wi-Fi isn't available, connect your device to iTunes.
5. Update your iPhone to the latest version of iOS.
6. Reset network settings by tapping Settings > General > Reset > Reset Network Settings. This will reset all network settings, including Bluetooth pairing records, Wi-Fi passwords, VPN, and APN settings.
7. Restore the iPhone.

Thanks for reaching out to Apple Support Communities.

Cheers,

Pedro.