Deleted Text Messages Reappear Again . . and again . . and again . . and again. . . .

This started about a year ago. Not sure if it was an upgrade that caused it? This happens on all of my devices: iPhone XR, MacBook Air (most recent XOS upgrade) and my iPad 5th Generation. All are up to date but this continues.

I slide the name and select DELETE. It disappears. Then, when I open up my text messages again, all of the ones I deleted are back there again. It's so annoying. I get Security Code messages, etc. and they all come back. Why? The only thing that keeps them away permanently is a reboot. I don't want to reboot several times a day though.

Am I missing something?

I don't want to loose many of my deleted conversations permanently, as I text with people in my business for scheduling etc. But, I don't want my work clients names sitting in my text message area. Certainly don't want to text them by mistake when I'm trying to text a friend or something. You know how that awful error can happen.

How do I get these text messages to delete and stay deleted until I want to start up the conversation again anew?

I hope someone can help. Trying to avoid an appointment at the Genius Bar for this one.

Thanks!