SMS Logs Showing Auto Response

Over the past two weeks we have started receiving SMS messages with the message “help”.  The inbound numbers are random and very infrequently the same.  The majority of the numbers being targeted are not published so am assuming a bad character somehow retrieved them.  In looking through the SMS logs concentrating on Company Numbers I am seeing the inbound text and then an immediate outbound text to that very number.  These Company Numbers are only monitored by myself and am not responding to these texts.  When logged into the app as admin I am not seeing any outbound text.  Also, the admin account receives other texts but am not seeing any similar auto response.

Any ideas why these auto responses are being generated?  

Thank you,

Susan