When Facebook bought WhatsApp two years ago, the swallowed-up messaging company said in a blog post that "respect for your privacy is coded into our DNA". The app didn't ask your real name, email address or home address. But they never said anything about sharing your phone number.
If you don't want Facebook to have your number, the good news is, existing users have a 30-day window to opt out of allowing Facebook access to their phone numbers once the update rolls out. By going to "settings" and then "account," within the app, you can change your preferences. As VentureBeat reports, instead of blindly accepting the terms and conditions agreement when you update the app, "you have to click 'read'. There you will see a control at the bottom of the screen inviting you to 'uncheck' the box giving your permission."
Here's what it looks like: