You can change your PIN code unlocking Surf anytime. If you forget the PIN code, you need to restore access to the wallet using the seed phrase and set the PIN code again.
To change the PIN code:
On the main screen of the application, tap the Surf icon in the upper left corner.
On the Settings screen, tap Safety protection.
On the Safety protection screen, tap Lock method.
Tap Change PIN.
Enter your current PIN code.
Enter the new PIN code and confirm it.