The traditional 4-6 digit numeric passcode found on most smartphones, including iPhones, can sometimes be a bit dull.

Here's a guide on how you can change your passcode to letters:

1. Open your iPhone and tap "Settings".
2. Tap "Face ID & Passcode".
3. Enter your current passcode.
4. Tap "Change Passcode".
5. Enter your current passcode again.
6. Then, tap "Passcode Options".
7. Tap "Custom Alphanumeric Code".
8. Choose your new passcode.
9. Confirm your new passcode.