Someone has been using my Apple id

Are you sure the message is legitimate? Does it contain a link for you to sign in somewhere? It may be a scam. Check your purchases history.

Purchase History Review

Apple won't send you an email/text telling you your account is disabled. You will find out the next time you try to log in somewhere.

Apple will always address you by your name or the name they have on file for you, not Dear Customer, Dear Client or by using your e-mail address.  The e-mail will be from @apple.com or @iTunes.com. E-mail addresses can be spoofed. You can go to Mail/View/Message/Show all Headers to see more. Apple e-mails will never contain an attachment. Apple will never request personal information such as Social Security numbers.

The only exception to the above I have noticed is if you order something from the Apple Store (apple.com), your receipt will be addressed to Dear Apple Customer. That is a receipt for a purchase you initiated.

Avoid phishing emails, fake ‘virus‘ alerts, phony support calls, and other scams

Identifying legitimate emails from the iTunes Store

Send the e-mail to Apple as an attachment to a new e-mail before deleting it. You can forward as an attachment by going to Mail/Message/Forward as attachment. You won’t receive a response.

 reportphishing@apple.com