I have helped many older ladies who fell for this or similar scam. They have likely installed remote software on your PC. Find someone who can clean this up for you. Malwarebytes is a good start (along with other anti-virus and similar), but you may want to even consider going back to a restore point.
You were smart not to pay. About half the ones I have help have already paid. But you still have to clean up. Good luck.
This is REQUIRED, not optional. They have already installed the remote control software ["She then had me go to www.fastheal.net and click on Technician No. 3 for remote access. Yes, I know I should not have done this. Technician performed a scan"].
It likely shows up as legitimate software, so anti-virus software will likely not even catch it.