Mary, I just looked at the messages we exchanged under the last Mudcat ID you used and see we corresponded about Facebook Messenger in 2020. You were extremely leery of Facebook and not answering messages. At the time your account was somehow compromised. And I can't remember what the oddball name was you were using instead of your own for your Facebook account.
If you are on a computer and can open Facebook then you can see the Messenger symbol at the top right of any page. It's the little text balloon with the angular squiggle.
How are the security settings on your Facebook account set? If you have it as "friends only" who can read your Facebook posts and have access set (for example) so only you can see your friends, then those are the people who are most likely to use Messenger to communicate privately.
Messenger is its own freestanding app in phones and tablets, but it is wedded to Facebook on computers. Where are you using it (somehow I don't visualize you texting a lot on a smartphone)? It is connected to your Facebook account so anyone who is a friend there can contact you. You can also communicate with others outside of your friends from posts you read on Facebook.
Is any of this at all helpful? Your best bet is to sit down side-by-side with someone well-versed in this and pull up your Facebook account and have them help you with the particulars.