If you need to unpair your Watch and don’t have access to your iPhone or can’t remember your Apple Watch passcode, follow these steps:
Put your Apple Watch on its charger
Press and hold the side button as if you were going to power it down
Do a firm press on the POWER OFF slider and let go
Tap Erase all content and settings
Alternately, you can go to Settings ? General ? Reset to erase and unpair your Apple Watch if you know your passcode, but the option above is faster.
If you need to erase and unpair your Apple Watch without your iPhone, you can log on to icloud.com and remove your Apple Watch under Account Settings ? My Devices.