Avast virus software Automatic update wiped out all of my files! Aurora Colorado

I just downloaded an avast automatic update, and after my computer restarted all of my files were gone!  All of my documents, pictures, and downloads.  

I called avast technical support, the woman told me it was malware that was already on my computer and that it would cost me $179.00 to repair it.  

If so, why did this antivirus software let that get on my computer?  

It's a toltal ripoff!  She said to call another support person if I didn't believe her.

Don't do the upgrade, and don't use Avast!