Serious help needed, as my browser is completely blocked

I"m running Avast but I am now getting a popup that says I have a virus. Over and over it says that and I cannot remove the popup from the screen, it is telling me to call Microsoft which I feel is bogus. If Avast didn’t pick up on it, is it a virus? Has anyone heard of this and can help me get rid of it. I had to close my browser using Task Mgr but whenever I reopen it’s still stuck on that pop up. I’m freaking out!

Thanks,
Cheryl :o

Virus and false-positive problems should be posted in Viruses and Worms forum section

At top in that forum section you find a how to get help guide https://forum.avast.com/index.php?topic=53253.0

Install unchecky. Check for any weird apps in add or remove or using ccleaner. Seems like an adware got into your system.