Threatened for a ********** account

A ********** account was opened at MTN in my wife's name. She started receiving sms's and calls about an amount owed to MTN from a company called VVM. We went to MTN headquarters and received a letter stating a ***** account was opened in her name. The gentleman assured us we should ignore these call's however they still continue. Please update the records accordingly. On three occasions I emailed the letter from MTN but they continue to send sms's and emails demanding money.