What to do if I receive payment wrongly in my account

I have received a payment from my client company in Qatar to my Indian Account. The company has a pending payment which is not paid to me since 2 years and they ignored my calls and never answered my request. So now they have made a wrong payment which is higher than my pending amount and now the concern person send me a mail to transfer those whole fund to a third party account in India. He called my once and asked me to transfer immediately to the third party account as I was outside i asked him to call later and after he never called me again. But I started receiving calls from his friends and others asking me to return the money to some other account, Since beginning I informed him to approach the concern bank about issue and to raise a complaint and once I receive the mail or call from my bank then I will give my consent to deduct the cash received. Now he is approaching through third party and abusing and giving death treats and trash my life if i dont transfer money to the third party account in India. I have not denied to refund the amount/I said will credit in to same account from where I received but I refused to pay on third party account. In this regard I request to provide me your valuable advise, as he is giving death treats/abusing what should I do in this case please advise Thanks & Regards Reyaz