my husband's computer on Microsoft has been disabled with Defender Smartscreen. How do I fix it?

No. That is a tech support scam, and it is not safe to call that number.

Microsoft states that:

• Microsoft will never proactively contact people with unsolicited technical support.
• Genuine Microsoft error and warning messages never include a phone number to call.
• If a pop-up or message tells someone to call support, the number should not be called.

What to do now:

1. Do not call the number.
2. Do not click links in the pop-up.
3. Close the browser window immediately. If the mouse cannot close it, try ALT+F4.
4. If the browser is stuck, restart the computer.
5. When reopening the browser, do not restore the previous session or previously open pages.
6. If any remote access software was installed or any credentials were entered, change passwords and check for unwanted software.
7. Report the scam to Microsoft using the official report form: Submit report

A real Defender SmartScreen warning is meant to warn about unrecognized apps, but Microsoft warning messages do not tell people to call a phone number. The phone number in that message is the clear sign that it is fraudulent.

References:

• Protect yourself from tech support scams
• Avoid and report Microsoft technical support scams
• Protect yourself from online scams and attacks
• Tech support scams