Yes, it is a hoax. The IRS does not communicate in that way. They would address you with certified mail and discuss options before they took such a measure. Do not answer the call. Give no private information. THey will steal everything in your account.
No, they do not use certified mail. They use regular USPS mail, with US Treasury Return address, sent to the address listed on the last 1040 you filed. People keep posting "certified" and that is not true. As a retired tax auditor of 30 years, I know since I've been responsible for thousands of those Regular USPS letters.
The Irs doesn't need certified to prove anything in order to hold you accountable. As long as you pay taxes, and live and breathe, they will find you.