For Online Computer Support, Ask a Computer Technician
what is the actual issue you are having problems with
and if you accepted an additional service for a phone cal it should give you a place to put your phone number
Probably was a scam especially if they called you to tell you about the problem they had to fix
Call the number on the back of your credit card and dispute the charges. They will put the money back in your account and probably issue you a new card so they can't charge you again
You should also run a virus protection program like malwarebytes to make sure that they can't get into your PC again without your knowledge.