Hi! I see you're getting a "carrier error" message in the YouMail app on your iPhone. To help you better, could you please tell me a bit more about the error? For example, does it say "carrier not supported," or mention an OCN (Operating Company Number) issue? Also, which carrier are you using?

In the meantime, here are some general steps to troubleshoot carrier errors in YouMail on iOS 18.7:

1. Check Carrier Support: Ensure your mobile carrier is supported by YouMail. Some carriers require manual activation or are not officially supported.

2. Verify Call Forwarding Settings: YouMail relies on Conditional Call Forwarding (busy, no answer, unreachable forwarding) to route calls. Sometimes your carrier needs to manually set this up. You can also try resetting call forwarding by dialing *73 to deactivate forwarding, then setting it up again through the app or carrier codes.

3. Manually Update Carrier Info in YouMail:
- Open the YouMail app.
- Go to Settings > Carrier Info.
- If your carrier is listed, select it manually.
- If not, try reinstalling the app to refresh carrier data.

4. Check SIM and Network:
- Restart your iPhone to refresh network connections.
- Remove and reinsert your SIM card.
- Confirm your mobile plan is active and supports voicemail service.

5. Activation Help:
- If the error persists, YouMail may require special activation codes from your carrier.
- Contact your carrier to ensure Conditional Call Forwarding is properly activated for your number.

If you can share your specific carrier or the exact error message, I can guide you further with more precise steps. Does any of this match what you see?

Looking forward to your reply so we can fix this!