Hi,
Thank you for writing to Microsoft Community Forums.
I understand that you are seeing duplicate messages in your phone app. I suggest you to refer the section Why are some of my text messages missing? from the article Your Phone app help and see if that helps.
I also suggest you to refer the section I've tried everything, but I'm still stuck. What should I do? from the above article.
Meanwhile, we are working on the app to make it better. We would like to hear your thoughts and suggestions, as there may be other users with a similar issue. Hence, I would suggest you to post a feedback in Microsoft Feedback Hub so that our developing team can review your suggestions and check if it can be included in the future updates.
Regards,
Nikhar Khare
Microsoft Community - Moderator