My iCloud is hacked?

Apple does not make such calls.

All such calls are scams from criminals attempting to steal your personal and financial information. The callers will often use number spoofing to pretend they are calling from a legitimate business. The correct course of action is to ignore the calls or hang up on them, repeatedly if needed. 

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

The majority or telephone calls received here are a scams, most of the arriving email is scams, the calling telephone numbers are routinely faked, sending email addresses are faked, and the calls about the car warranty or the outstanding arrest warrant or the tax debts or the relative of mine in a far away place that needs bail money or the prince that needs a recipient for a wealth transfer or the calls for the church or the fire department or the police department collections are... scams.

There are scam pop-ups and scam calendar subscriptions and scam advertisements all over the network, too.

These scams work.

Scammers and advertisers absolutely and intentionally use words that scare, too. HACK. VIRUS. INFECTED. ARREST. Those and other words work on a lot of people, too. They cause the folks to stop thinking, and start doing what the scammers or advertisers want them to do. Which is generally not in the best interests of anybody other than the scammers or advertisers, or in the interest of anyone other than the politicians and their patrons, with propaganda.

Scam Pop-ups, Scam Viruses, Scam Receipts… - Apple Community

Yes, it is a scam.