irritating virus warning pop up
My iMac has been infected with some pop up advertisement that insists that I call there Mac Support Virus Removal Malware Support phone number because my iMac has been infected with a virus and it claims that I need to be shown how to disable pop ups. My pop ups ARE disabled in Safari preferences and the only pop up that is irritating me is this insistant ad that opens up growers pages and pop up windows to warn me and insist that I call their number. I finally called and they wanted to scan my computer and then assess the fee to "fix" it. How do I get rid of this constant sales pitch to call them or should I be concerned!?
iMac, OS X Yosemite (10.10)