Do you have such a case? If not, then you received a phishing/scam attempt and, thus, is not legit. From what you say, you have not yet provided any sensitive information to anyone. If I am, correct then that is good. If you did provide sensitive information to someone, then your may need to:
Follow up, for example, with a credit card company, Apple, Social Security, your bank, etc. or to
Change your Apple ID password https://support.apple.com/en-us/HT201355
And, here is What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071
This information should help you. See the last item listed especially, the per Eric Root one.
If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement https://support.apple.com/en-us/HT201382
Identify legitimate emails from the App Store or iTunes Store https://support.apple.com/en-us/HT201679
How to avoid scams when using Apple Pay to send and receive money https://support.apple.com/en-us/HT208226
Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams https://support.apple.com/en-us/HT204759
How to identify scams related to purported apple email notifications—per Eric Root.
“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 emails won't have poor grammar/misspellings. Apple e-mails will never contain an attachment. Apple will never request personal information by email such as Social Security numbers, your Mother’s maiden name or full credit card 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.”