Removing a phone number from a lost Apple Watch

You will need to contact your cellular carrier to have the phone number disconnected. Neither you nor Apple can do this. If you ever find your watch you will need to contact your cellular carrier to reestablish a phone number. Of course this assumes you are referring to a cellular enabled Apple Watch that has its own phone number. And the actual phone number of your Apple Watch is irrelevant because it is tied to the phone number on your iPhone. Just establish a new number on the new watch.

Let’s try again. When you unpair your lost watch from your iPhone you will asked if you want to keep your cellular account. Answer YES and continue with the unpairing. When you pair your new watch to your iPhone your cellular account will be transferred to the new watch with the same phone number. You do this yourself. If you want a different phone number for your new watch then call your carrier and ask for that.