code: public void cancelSubscription() throws NotConnectedException, InterruptedException {
          Presence unsubscribed = new Presence(item.getJid(), Type.unsubscribed);
          connection().sendStanza(unsubscribed);
      }
docs: Cancel the presence subscription the XMPP entity representing this roster entry has with us.
  
  @throws NotConnectedException
  @throws InterruptedException
  @since 4.2