Sender's text message included phone numbers that were not in senders contact list

[Judith55]

I have a new S21 5G (not Ultra) and a new service carrier. I received a text from a contact in my list. Included in the list of those in the group for this text were 2 contacts from my contact list. These 2 contacts are not in the sender's contact list nor is there any reason for them to be the sender's contact list. The Sender has an Apple phone. My message app that this occurred on is the default Samsung Message app. Since this occurred, I installed the Google Message app and changed the default to Google Message. I chatted with a Samsung rep this morning and their comment was that this is a carrier issue. I don't understand why that would be. I contacted my carrier and they said it isn't their issue.  Any thoughts out there on how this occurred? Spam / hackers?

[Pugs1957]

Any chance you could post a screenshot with any personal information deleted?

[Judith55]

Not  having luck with a screenshot. There's not much to the text. The content of the text shows (1KB) and next to it is MMS 12:59 PM. The recipient list shows 5 recipients. 

Finally made this work. Here's the thread...