How to unpair the Apple watch when the paired phone is no longer available?

From a web browser,sign in to iCloud.com with your Apple ID.

Go to Find iPhone.

Click All Devices at the top of the screen.

Click your Apple Watch.

Click Erase [device]. Select Next until the device is erased.

Click Remove from Account.

Then see this;

How to pair your Apple Watch with a new iPhone

I’ve gone to iCloud.com, and the device is no longer listed the I watch that is, the password on the IWatch won’t let me in, I’ve contacted Apple support, they are not able to help me. The watch is less than a year old and I’ve only used it maybe a half a dozen times. I think it’s still linked to another iPhone how do I unlink it? I did purchase a new Apple Watch, I was able to set that one up, and in the section where it wanted me to sync, it listed all of my I watch that I’ve ever had, How do I get to that screen again? Then going around in circles

how do I UNPAIR MY APPLE WATCH FROM MY IPHONE

The post above yours tells you how to do it.