1-800-MY-APPLE is a legit Apple phone number. But, there are cybercriminals who are calling their potential victims and spoofing their telephone numbers to make them appear as if they calling from 1800MYAPPLE. The callers (cybercriminals) will say your account has been compromised and will instruct you to go a Remote Access website so they may gain access to your computer in order to help you remotely.
But, there is never any danger to your computer, unless you follow the caller's instructions. If you get an unsolicited call from someone claiming to be from Apple, hang up and contact Apple directly. And, Apple will never ask you to provide information like passwords, verifications, or security keys over the phone.
If you think you have fallen victim to the scam, please remove any software you were instructed to install, change your Apple and computer passwords.