Q: I have a new phone number. The number saved in my Account information is not valid anymore. How do I change my phone number in order to be able to access the iCloud Keychain??

Hello CAM231290, 

Thanks for using the Apple Support Communities!

I understand that you need to change the phone number associated with your iCloud Keychain. The following article explains how to do this. 

1. Make sure that the correct phone number is associated with your account: 
    
   • On your iPhone, iPad, or iPod touch, tap Settings > iCloud > Keychain > Advanced. (In iOS 7, tap Settings > iCloud > Account > Keychain.) Make sure the phone number under Verification Number is correct. If not, enter another phone number. 
    
   • On your Mac, choose Apple menu > System Preferences. Click iCloud, then click Options next to Keychain. (In OS X Mavericks or earlier, click iCloud, then click Account Details.) Make sure the phone number under Verification number is correct. If not, enter another phone number.

If you can't access a device that has iCloud Keychain enabled, contact Apple Support and verify your identity to get help setting up iCloud Keychain.

Get help using iCloud Keychain - Apple Support

Cheers!