Someone used my email and created an apple ID. How to unlink that ID from my email?

If necessary, contact Apple ID Support for assistance.  See the Apple Support articles below for contact information.  

Apple ID - Official Apple Support.   -

Contact Apple for help with Apple ID account security - Apple Support.  *   (Link doesn’t always load)  

Get Support      -    Work through the screens to get a chat option. You may have to pick a slightly different problem.

Apple Support schedule phone call.   -

If necessary, try Twitter

https://twitter.com/AppleSupport.    -          

From the Apple Support article below. 

Without proof of your identity via security questions and other carefully selected criteria, Apple Support can't help you reset a password or perform any other actions on your account. These policies are audited and reviewed on a regular basis.

Security and your Apple ID - Apple Support.      *

Also, secure your email account. In order to successfully create an AppleID with your email account, they have to be able to read your emails to respond to the confirmation link necessary to finish setting up an AppleID. So someone has access to your email account.

You can use the forgot password button on any ‘Sign In with Apple ID’ page to have an email sent to yourself. You can then use a new password to remove them or do whatever you want with the Apple ID.