Reserve service is a joke

Normally I am very happy with Uber and I prefer to use direct channels to complain. The reason for the 1 star is that I simply cannot find anywhere to register the issue and get feedback. I used their Reserve service - one they're perpetually advertising for seamless planning - for a trip to the airport. Only when I hadn't received any notification of imminent arrival at the appointed time did I go into the app and find out it had simply been cancelled. No notification, no warning, and no explanation. So what's the point of booking in advance? Don't offer a service you cannot fulfil.