Q: When setting up Keychain to work with other devices, it sends a verification code to a phone number I've never owned. How can I change the default phone number?

Hey there bighelpseeker,

It sounds like you need to update the phone number associated with your iCloud Keychain. Check out this info from the article named:

iCloud: Troubleshooting iCloud Keychain

http://support.apple.com/kb/TS4644

• Check that you have the correct phone number associated with your account:
  • Devices using iOS 7.0.3 or later: Tap Settings > iCloud > Account, then tap Keychain. Check that the phone number listed under Verification Number is correct. If not, enter another phone number.
  • Macs using OS X Mavericks v10.9 or later: Choose Apple () menu > System Preferences. Click iCloud, then click Account Details. Check that the phone number listed under Verification number is correct. If not, enter another phone number.

Thank you for using Apple Support Communities.

Cheers,

Sterling