Hello TinaNZ,
Welcome to Apple Support Communities. So we can clarify, are you having this trouble using the Messages app on your iPhone? Or are you using a third-party app like FaceBook Messenger? If so, we suggest updating the Messenger app you are using to help with this issue. The steps to do so are listed in the Apple Support article:
How to manually update apps on your Apple device - Apple Support
How to manually update apps on your iPhone or iPad
1.Open the App Store.
2.Tap your profile icon at the top of the screen.
3.Scroll to see pending updates and release notes. Tap Update next to an app to update only that app, or tap Update All.
Let us know if this helps, or if you're having a different issue.
We look forward to hearing back from you.