Clear phone call history Apple Watch 4

I was just able to do that on my iPhone and it cleared Recents on my Watch. Try resetting the Watch to be sure it is connecting to the iPhone. Press and hold the Digital Crown and power button together until you see the Apple logo and then release. The Watch should reboot. After unlocking the watch, go to the Phone app on the iPhone and see if Recents is clear on the iPhone, then check the Watch.

Thank you. Given that you have tried everything, your next stop is Apple Support. No one here could advise you of anything else since your post has indicated all of the user troubleshooting steps.

The method described by julieda works for recent calls on my  Watch. Try resetting your  Watch then try the deletions again. To reset you  Watch press and hold both the Digital Crown and Side button simultaneously. Keep pressing until the Apple logo appears on your watch. Then release the buttons and let the watch restart.

1. Open the Phone App (Phone Icon on iPhone), then tap Recents to view a list of recent calls.
2. Tap Edit.
3. Delete your entire call history or a specific call. To clear all history, tap Clear, then tap Clear All Recents. To clear a single call, tap the Delete button , then tap Delete.