*Who* says you have been “hacked”?
If it is somebody on the phone that called you…it is a fraud. No "ifs", "ands" or "buts" -- it is a fraud. Do not engage, just hang up. Do not answer if they get aggressive. They are all based overseas so the cops do not get involved. They call *everybody* hoping to catch some “phish.”
If it is a web page that happened to pop-up…it is a fraud. These are infected websites (not your computer) that again want to ‘fix your computer’ for a fee. Same goes for emails that you may have received. In fact, *anything* that says ‘call this number’ or ‘click this link’ is very likely a fraud.
Now more questions:
Assuming you are running Windows, which version (Could be XP, Vista, 7, 8 or 10.)?
Which Antivirus program are you running?
Is your operating system (i.e., “Windows”) and Antivirus program updated?
What happened that caused you to ask the question about repair?
Your computer may or may not require fixing, and someone may be able to help you fix it yourself. If it appears as a message on your computer screen, a ‘screen shot’ (a picture of the screen) would help us figure that out.