If equipped, remove, and then, re-install the SIM card.
Restore your iPhone: To restore your iPhone, connect it to your computer. When the iPhone appears in the iTunes source list, click the Restore button on the Summary tab. (Note: The following will erase all of your data and media and resets all of the iPhone's settings. You will need to restore it from a previous backup from either iTunes or iCloud. Note: If you are running macOS Catalina, you will perform the same task using the Finder app instead of iTunes.)
If equipped, remove, and then, re-install the SIM card.
Restore your iPhone: To restore your iPhone, connect it to your computer. When the iPhone appears in the iTunes source list, click the Restore button on the Summary tab. (Note: The following will erase all of your data and media and resets all of the iPhone's settings. You will need to restore it from a previous backup from either iTunes or iCloud. Note: If you are running macOS Catalina, you will perform the same task using the Finder app instead of iTunes.)