If you need to remove a Switch+ from your account, login to the ecobee app with your username and password and do the following:
1) Select your Switch+ from the list by tapping it. You may need to tap "Switches" in the bottom right to switch from Thermostats view to Switches view
2) Tap the Main Menu icon in the bottom left and then tap About
3) Tap "Remove Device from Account" and then "Remove" to confirm
NOTE: If your Switch+ is offline, you'll see the following screen instead when you get to Step 2. In this case, tap "Need Help?" and then "Remove Device From Account"