I had this happen it's a total scam! The sad/scary thing is some older people may take it serious and fall for it. When this happen to me before I actually answered one of their calls and told them that I turned them in and they better never call me again I also let them know that the IRS doesn't call people. What happened next was a click! they hung up. It was a Spanish mans voice that time.
214-295-2866 keeps calling me and saying the are the IRS and do not disregard this voicemail. The IRS would send me a letter and not call me harassing me!