Hello JillyCoop,
It seems like you want to stop reminders to end your workout, correct? We'd like to provide some information.
If you want to turn workout reminders off, please check out this link, which explains how to do that, and may help: Adjust the workout settings on Apple Watch
Turn workout reminders on or off
For walking, running, swimming, and other workouts, your Apple Watch senses when you’re moving and alerts you to start the Workout app. It even gives you credit for the exercise you’ve already done. It will also remind you to end your workout, in case you get distracted when you’re cooling down. Follow these steps to turn workout reminders on or off.
1. Open the Settings app on your Apple Watch.
2. Tap Workout, then change the Start Workout Reminder and End Workout Reminder settings. (Workout reminders are on by default.)
You can also open the Apple Watch app on your iPhone, tap My Watch, tap Workout, then change the workout reminder settings.
If you need additional assistance, please contact Apple Support for help. You might be able to reach them here: Contact Apple Support
Thanks!