My whatsapp tone will not change back after update

Sorry to hear that the WhatsApp site's fix didn't work, cazrose. We'll be glad to help you get that working again.
Make sure all of the applications on your iPhone are up-to-date:

On your iPhone, iPad, or iPod Touch:

• Open the App Store app.
• Tap Updates.
• Update all or each one at a time.

Test your ability to change the WhatsApp ringtone. If it's still now working, next we will reinstall the application. Use the Delete and reinstall the app section of this article to do so. Please note you should make sure WhatsApp is backing up your chat archives first:

If an app you installed unexpectedly quits, stops responding, or won’t open

If the issue still persists, then use these steps to troubleshoot the iOS installation:
1. How to back up your iPhone, iPad, and iPod touch -- Make sure you have a recent backup of your phone to be sure your personal information is safe.
2. Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings -- This process will completely wipe the iPhone to allow a fresh copy of the iOS to be installed.
The first time through, select "Set up as a new iPhone". Feel free to sign into iTunes & App Store and iCloud. Download the WhatsApp application and see if you're able to change the ringtone. If you're able, continue with the next step.
3. Restore your iPhone, iPad, or iPod touch from a backup -- Use this article to guide you through the process of replacing your personal information back on your phone. Remember to test again after this last step as well.

Let us know how this works. Thanks and have a great day!

My ringtone in WhatsApp has changed too since the update, but in the actual WhatsApp settings it's still set to my original tone of 'Note'. I use WhatsApp a lot with family messaging and had this set differently so I knew exactly when it was WhatsApp message and not SMS. Is Apple going to fix this so I can use my original tone?

Greetings, cazrose. Thanks for joining Apple Support Communities!
I see that WhatsApp isn't allowing you to change it's ringtone back to what it was after upgrading your iPhone 6s to iOS 10. I'll be glad to help!
How do I change my ringtone for WhatsApp? -- Follow the support instructions I located on the WhatsApp site.

Have a great day!