I've been using RingCentral for several weeks now. I noticed that incoming calls from numbers that were not in my contacts list showed up as "Unknown". When I chatted with tech support to find out why Caller ID wasn't working for incoming calls, I was told for the first time (since it doesn't appear in the "features" description) that I would have to upgrade to at least a Premium plan. This would cost me $540 a year for RingCentral to provide what the phone company already provides for free. I really don't need any of the features in the other plans, and had absolutely no idea when I signed up that Caller ID would be an upcharge.
This should be a basic feature for all plans. Its lack in Essentials and Standard is inexplicable.