OK, called FIDO tech support today, and they feel that it is an app that is responsible for these messages. FIDO had several on their list, one of which is the Samsung Messages app. However, they had over a dozen on their list, so it could be any or all of them.
The thing I don't get is that I have push messaging turned off, and I still get them.
FWIW, I left the most recent one on my phone, and never opened it. I have received no more since. I am going to just let it work its way to the bottom of my list of messages, and leave it there. Perhaps that will stop any further ones from coming through.
Please note that I have not opened ANY of these messages, so I don't know if there is malware attached to them or not. Perhaps it is legitimate. However, at this point I don't know, and therefore I will not open one to find out.
Frank.