Thanks for the replies. On the phone, I must have used a different ID at one time in the past. On the phone, when I am at the prompt "Signing in to your account...." it shows the ID but I don't have option to sign into a different account. The only option is "enter password or forget password" to that ID.
The Watch is brand new and sealed. This is the first time of pairing the Watch to this phone. I am not sure how it could be locked to a different ID.
(1)we know a brand new, out of the box Apple Watch would not be previously paired. (2) The iPhone you are using is currently signed into your Apple/ICloud account. (3) After you start pairing the Watch to the iPhone, it IPhone auto fills with an AppleID you “must have used a different AppleID at one time”.
-unpair the Watch from your iPhone.
-enter the PIN code on the watch.
-Tap Settings
-Tap General
-Tap Reset
-Tap Erase All Content and Settings
-Tap Erase All
Retry the pairing process over again. Important note, this reset does not remove activation lock. If the watch was a previously owned-private sale and the watch never had activation lock removed before selling to you, immediately contact the seller and have them remove activation lock or refund your money. iPhones, iPads, watches going from part A to party b where party a never removes activation lock? Party b now has an expensive paperweight. It may seem stringent but it makes stolen devices near worthless unless someone buys it without knowing about activation lock.