Hi Court1980_,
Thanks for reaching out in the Apple Support Communities. We understand that you're concerned that your iPhone may be compromised. You mentioned that your former significant other had created an action where a message would appear when you connect your phone to power.
This sounds like they may have previously created a personal automation in the Shortcut app of your iPhone. To check to see if this is true and how to disable it, follow the steps in Enable or disable a personal automation.
To learn more about the Shortcut app and what you can do with it, check out Shortcuts User Guide.
However, if you believe that your device or Apple ID have been compromised, you'll want to review these support articles below:
If you think your Apple ID has been compromised
Checklist: If you want to see if anyone else has access to your device or accounts
All the best.