They can't actually recover any amount from you, which at first place was obtained by you without keeping them in dark or without playing a fraud upon. Thus, meaning there by, if your claims were genuine and released in good faith by the company, that are legally not compete to seek a refund of the same from you at this stage.
You may turn down their request. You're competent to do this. In case they take a legal recourse, this may be keenly de defended in a court of law.