Dear Jonathon Bates,
Hello! Welcome to the Microsoft Community.
I understand you are having issues with the Phone Link app. It looks like you are receiving duplicates of messages you sent. I understand and I will do my best to help.
Please check your app version, is it up to date? This could be a problem with a specific version of Phone Link. It could also be a problem with the latest version of the app. We haven't identified the issue yet. But there have been a lot of issues with the Phone Link app lately.
If you are on the latest version and have this issue, I would recommend trying an older version of the app to see if it has the same issue.
Go to the website hereand type in the following link, you should see a lot of different versions of the install package, select the older version to download.
https://apps.microsoft.com/detail/9nmpj99vjbwv?rtc=1&hl=en-US&gl=en
Disclaimer: This is a non-Microsoft website. The page appears to be providing accurate and safe information. Watch out for ads on the site that may advertise products frequently classified as PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
In addition, we sincerely recommend that you report the problem to Microsoft. Press "WIN + F" to open the Feedback Center. You can describe the problem in detail with pictures. Your feedback can help Microsoft better understand the problem. Thank you for your understanding!
If you have any progress, please let me know at any time.
Best Wishes
Pyke.D | Microsoft Community Support Specialist