Hello! I see you're getting an "On register 503" error when trying to make international calls using the Mytello app. Let's get to the bottom of this together.

First, just to clarify, does this error happen every time you try to place an international call, or only to specific countries or numbers? Also, do you see this error message immediately after dialing, or during the app registration/startup?

Meanwhile, here's a common approach to fixing this issue:

1. Check Network Connection: Ensure your Android device (Android 15) has a stable internet connection—WiFi or cellular data—since Mytello relies on internet connectivity for calls.

2. Restart the Mytello App: Fully close the app and relaunch it to refresh the registration process.

3. Re-register the App:
- Go to the app settings.
- Look for an option like "Account" or "SIP Registration."
- Logout and then log back in with your credentials. This forces the app to re-establish connection to the service.

4. Verify Your Account Status: Sometimes the 503 error can indicate a problem on the server side or account suspension/block. Log into your Mytello account on their website to confirm your account is active and in good standing.

5. Check Dialing Format: Confirm you are dialing the international number including the correct country code (starting with '+') without extra zeroes or zeros after the country code.

6. Clear App Cache:
- Go to Android Settings > Apps > Mytello.
- Tap Storage > Clear Cache.
- Relaunch the app.

7. Restart Your Phone: Simple but often effective.

If none of these steps resolve the issue, it may be related to temporary server issues or restrictions on international calling from your account. Mytello's servers might be overloaded or undergoing maintenance, triggering a 503 "Service Unavailable" error.

In that case, check if the problem persists after some time or contact Mytello support at [email protected] for account-specific assistance.

Would you like me to walk you through any of these steps in detail? Also, please let me know what you've tried already!

Are you satisfied with this initial guidance so far?