Threatening Emails

My wife got this sms and email from LoanSA stating that she own them R1806.81 for taking out some service thing with them and my wife knows nothing about this matter. When I asked for proof of this transaction, they said that she made it by electronic application, it got all the details of my wife but the banking details isn't that of my wife. I have asked for any written proof of any application and where she signed for any of this loan or service, but they can't provide any....When I told them that someone stole the ID details of my wife, they just kept on sending threatening emails. Then she started getting emails from Lifestyle Legal telling her to pay up or she will get a summons from the court and the sheriff and that they will blacklist her at the credit bureau. She haven't asked or apply for any loan or any service from Loan SA and now these companies are making my wife's live a living hell and I are on the receiving end of all this what can we do????