TRUWORTHS allows threatening sms's

I receive weekly sms's from a debt collecting company MBD with threatening messages about an unsettled TRUWORTHS account. I don't buy at TRUWORTHS and don't have an account!!! MBD says there is nothing they can do - TRUWORTHS is their client. After numerous calls to TRUWORTHS, confirming that I DO NOT HAVE AN ACCOUNT, I still receive the sms's and they refuse or are incapable to do something about it