A -----
    Put your watch on its charger and keep it there until you complete these steps.
    Press and hold the side button until you see Power Off.
    Press and hold the Digital Crown until you see Erase all content and settings.
    Tap Reset, then tap Reset again to confirm.
    Wait for the process to finish, then set up your Apple Watch again. When asked, restore from a backup.

B----
To unpair and erase watch and remove Activation Lock.

On a computer, go to iCloud.com and sign in with your Apple ID. 

Go to Find Iphone.

Select All Devices, then click your Apple Watch.

Click Erase Apple Watch. 

Select Next until the device is erased.

Click the remove button next to your Apple Watch.

I tried them both and they did not work