Q: Is my computer safe or it is compromise?

It's a scam.

If you are using Safari, go to the Safari menu bar, click Safari > Preferences then select the Privacy tab  then click: Remove All Website Data then quit and relaunch Safari while holding down the Shift key.

Anti virus software is useless on a Mac.

The best way to avoid scams is to keep your Mac's OS X software up to date.

Sorry, but you have been scammed. Any such pop up message will always be a scam. Unfortunately, you have allowed the criminals to access your computer. Please contact your bank and dispute the charge, and inform them of the fraud. Then restore your computer, using a backup that predates the criminal act.

Please read Phony "tech support" / "ransomware" popups and web pages.

By allowing criminals to access and use your Mac, it should no longer be considered secure.

Your actions at this point can range from doing nothing at all, to erasing the Mac and reconfiguring it. Separately, it would be prudent to assume the intruder has gained sufficient information from it to effectively commit identity theft. Computer tampering and identity theft are legal matters that go well beyond the scope of this support site, and for which you should seek appropriate legal counsel. Therefore I can only offer technical guidance regarding your Mac itself, which may be considered evidence in a criminal proceeding that only you can decide to take upon receiving that counsel.

At a minimum it should be immediately disconnected from the Internet (unplug its Ethernet cable and turn Wi-Fi "off") after which you can decide whether to preserve it in its present condition as evidence, or its contents completely erased, permanently removing that evidence. Decide how you want to proceed and write back.

Yes.

Unauthorized use of someone else's computer is a crime, and has been for many years. If you are in the United States, consider filing a complaint with the FBI: https://www.ic3.gov/complaint/default.aspx/. Elsewhere, research a similarly qualified law enforcement agency, or even your local police. Although it is very likely the people committing these crimes are outside their jurisdiction, reports such as yours can be useful in addressing similar criminal activity.

It's very disheartening to hear stories such as yours. Although it is very likely that the criminals are simply looking to make a quick buck, it would be irresponsible of me or anyone else to say there is nothing else to worry about. Having allowed unauthorized access to your Mac, there is no way I would be satisfied with anything less than erasing it completely. That choice is yours to make.

You are also very likely to get your $299 charge reversed by calling your bank or credit card issuer, depending on how you paid. This is an obvious case of fraud.

Other than that, you can help others by telling them about this common scam. It's just a 21st century version of similar confidence schemes that have existed forever. Take that User Tip, forward it, email it, print it, or mail it to anyone else you know who could use it.