How to change piano key size on GarageBand Smart Piano?

How do I text Apple Support via iMessage on iPad (iOS 26.1)? The Apple Support app won’t let me text them because of my issue, which is just about GarageBand accessibility. I tried Google, won’t help, never helps. If Apple can reply to this message, my issue is: How to change the size of the piano keys on GarageBand’s Smart Piano?