Mobile phone number - Validate, update and remove SMS

To register and validate your mobile number:
Log in to your account, and follow these steps:

Settings → Account Details → Phone → Validate SMS

Then enter your mobile phone number and press 'Save'.

You should receive an SMS containing a code, which you should enter into the Validation Code screen and press 'Validate'.

To update your current number:
Settings → Account Details → Phone

Then update the mobile phone number which was previously validated and press 'Apply'.

To opt-out:
Settings → Account Details → Phone

Then remove your mobile phone number which was previously validated.