Issue with messaging app

[Android Central Question]

I have a Galaxy S9 and recently wanted to switch messaging apps to I switched from the Messages app (which I assume is the Samsung message app) to Android messages. Then all of my contacts re-received old messages that I previously sent them, including pictures, etc. I then switched back to the Messages app and I re-received previous messages. I would like to use the Android Messages app but I don't want to resend all my messages again so does any one know how to avoid this or why this happened in the first place?