If your iPhone is displaying No Service while using your ZIP SIM card in the US (and within coverage), the issue may specific to your device and not the ZIP SIM or service.
This issues has been acknowledged by Apple
iPhone may display one of the following symptoms in the status bar:
- Displays No Service or Searching in an area of good coverage
- Does not regain service when returning to an area of coverage
If you encounter any of the above symptoms on your iPhone, try these steps to attempt to resolve the issue. Test after each step.
- Try turning iPhone off and then on again. 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.
- Check for a carrier settings update. Tap Settings > General > About while connected to a Wi-Fi network. If an update is available, a prompt should appear soon. If Wi-Fi is not available, connect your device to iTunes.
- Update your iPhone to the latest version of iOS.
- Restore the iPhone.
Please visit the Apple Knowledge Base for more information and instructions.