If Apple has removed the malware, your computer's safe. BUT just in case you need to go in and change all of the PIN numbers and passwords associated with your various accounts, just in case they got some information from the malware while it was still in there. You are also going to want to monitor your bank account and credit card accounts carefully for unauthorized charges. If you charged the payment to the scammer to a credit or debit card, you should cancel that card and open up a new one.
Then you'll be safe.
As far as anything else is concerned, you don't owe these people anything. They are scammers and you are not required to continue the service. Your contract with them wasn't valid in the first place. Report them to your police, to the FBI online at their Internet Crime Complaint Center at IC3.gov and to the Federal Trade Commission at FTC.gov, so that if these folks have a website, the government can shut them down.
These types of scammers operate from abroad and aren't subject to the Do Not Call Register. Nor are they afraid of harassment charges, as they know you can't really find them. So block their calls. Ignoring them is the best way to make them go away. Eventually, when they see that there's no money they can gain from you any more, they will move on to someone else they can still scam.