"iCloud security breach" phone call

It's a scam.

About Email and Other Scams

Apple always addresses you by your name or the name they have on file for you.  The Email will be from apple.com or itunes.com. Email addresses can be spoofed. You can go to Mail > View > Message > Show all Headers to see more. Apple Emails will never contain an attachment. Apple will never request personal information such as Social Security numbers.

An exception to the above is when you order something from the Apple Store. The receipt will be addressed to Dear Apple Customer.

Avoid Scams

1. Identify and report phishing emails and other suspicious messages
2. Annual Reminder- Watch out for email Phishing Scams
3. Identifying fraudulent "phishing" email
4. Beware of Browser Pop-Up Tech Support, Phishing Scams
5. Phishing & Other Suspicious Emails
6. Avoid phishing emails, fake 'virus' alerts, phony support calls, & other scams
7. Phony "tech support" - "ransomware" popups and ... | Communities

Report phishing email to abuse@apple.com.

All calls like the one you received are scams/phishing attempts. They are made by criminals that prey on the unwary. Apple never would make a call like this. Apple only calls if a user if the user has arranged the call. 

And, there are things you can do to lessen the annoyance of such calls. For example, I hardy answer my land or iPhone any more. I only answer if caller ID or my contact list shows that I probably know the caller. Also, I figure that anyone that know me will leave a message if they have anything important to say and I don't answer.

And, if you want to, you can get a land-line system that you can use in blocking scam/spam calls. Also, I think this Apple document can be used to block scam calls as well as spam calls: Detect and block spam phone calls https://support.apple.com/en-us/HT207099

Scam. Apple will never call you unless you called them and asked for a call back.

you can be 100% sure