You can easily cancel BT Privacy at Home or Caller Display online. Go to www.bt.com/callingfeatures and click the Change your calling features button. This will start an online order process. Put in your home number and postcode and confirm you're the BT account holder to continue.
The next screen will show any calling features that are currently on your line. To cancel BT Privacy at Home or Caller Display just click the relevant box.
Click Continue to complete the cancellation order.
You can also manage all your calling features (including ordering, upgrading and cancelling them) at www.bt.com/mybt >