Hi! I understand you're able to use the Avant app for everything except paying for a ticket. Let’s get to the bottom of this so you can complete your purchase smoothly.

Could you please share a bit more detail about the issue? For example:
- Are you seeing any error messages when you try to pay?
- Is the payment option not responding, or does it fail after you enter your payment details?
- Have you successfully made payments in the app before, or is this the first time?
- Are you using a credit card or debit card, and is that card linked properly in the app?

Meanwhile, I can guide you through some common steps that often resolve these payment issues:

1. Verify Card Details and Funds:
Double-check that the card information entered is correct and that your card is activated with sufficient funds or credit available. Sometimes payments fail due to insufficient balance or exceeded limits.

2. Restart the App and Device:
Close the Avant app completely and restart your iPhone. Then reopen the app and try again. This refresh can clear minor glitches.

3. Update the App:
Ensure your Avant app is updated to the latest version available from the App Store, as that may fix bugs affecting payments.

4. Check Network Connection:
A stable internet connection is needed for payment processing. Try switching between Wi-Fi and mobile data.

5. Clear Cache and Re-login:
If possible, log out of your Avant account in the app, then log back in to refresh your session.

If you have already tried some of these, please let me know which ones so I can suggest more specific checks or escalate if needed.

Are you comfortable trying these steps now? Also, any specific error details you can provide will be very helpful!