Please try the following steps:
1．Confirm that your device is SIM-free or unlocked.
2．Go to Settings > General > About.
3．If prompted for a carrier update, proceed with the update.
4．Go to Settings > General > Software Update, and make sure your iOS is up to date.
5．Go to Settings > General > Reset > Reset Network Settings
(Note: This will also reset Wi-Fi passwords and other network settings.)
If the issue remains unresolved, please contact us via the “Post-Purchase Form” on the Help & Support page of our website.
