Scammer takes control of iMac through infected Canon printer driver

I have problems with the scanner part of my Canon printer. I opened up what I believed to be Canon website. Cutting a long story short the ‘engineer’ told me that the scanner driver had been infected by spyware. After. Providing personal details, but before my bank details I realised that the engineer had sent a small program to update driver, which allowed him to take control of the computer (2013 iMac). When the subject of money came up I noticed that the site was not secure and when I tried to shutdown the cursor immediately moved to prevent that selection. To avoid anything further happening I disconnected the power supply

[Re-Titled by Moderator]

Original Title: Almost scammed