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What "security scan" was this?
Download, update and run a full scan using the FREE version of THIS tool and let it remove anything it finds. Reboot if it asks you to in order to complete the removal of any malware it may have found.
To get your credit card number they would have had to have unfettered access into your bank account or to somewhere where you have the credit card information stored, make sure all online accounts and any desktop applications containing personal information have strong passwords, also make sure your computer has passworded access only. I find it hard to believe that any reputable bank/credit card company would not automatically reverse any charge you object to especially when it is an unsigned transaction. I suggest you call then back and ask to speak to a higher authority if they don't do that.
Be extra careful what you click on and what you download and/or file share in future.
Please advise what operating system and service pack you are using and what McAfee products and versions. (Double-click the taskbar icon to open McAfee and then click Navigate (top-right), then About).