Stop text from email addresses

Hello,

My wife is getting 30-50 spam text messages a day, but they are not coming from a phone number they are coming from some kind of fraudulent spam service using fake email addresses.  We have never clicked on them or responded to them we just want them to stop.  She does not want to change her number as she uses it for her home based business.  I did some reading online and it seemed there used to be a feature on ATT mymessages that allowed you to turn off receiving text from email address.  However since they changed it from mymessages to message.att.net, it seems this feature is no longer available.  How can I turn off receiving all text messages coming from an email address?  We went to the ATT store and that kid was not helpful, he insisted that my wife must be receiving them in her email too, which she is NOT, and he turn off some kind of syncing with her email address.  This has nothing to do with her personnel email address this has to do with the phonenumber@txt.att.net email address, we do not use this and just want to turn off receiving all text to this address. Any help would be greatly appreciated.

Thank you.