The Fitbit Community is a gathering place for real people who wish to exchange ideas, solutions, tips, techniques, and insight about the Fitbit products and services they love. By joining our Community, you agree to uphold these guidelines, so please take a moment to look them over.
I don't think you can turn stairs off, but stairs are not used in any calorie calculations. If you climb stairs, your heart rate will probably go up, and will will increase you calorie burn, not the stairs themselves.
Before posting, re-read to see if it would make sense to someone else not looking at your Fitbit or phone.