If you want to change or remove your old band, simply go to your Dashboard and navigate to "Explore" → "Settings" → "Connectivity & Data source".
You will have two options:
Remove band (this will delete the existing paired band from the app and our database).
Change band (this will change your band to a new one).
If you press on "Change band" you'll see listed all the X-Wrist bands available near you.
A "Connected" status will appear on the menu and the dashboard.