Call Back Feature

I don't think that this is supported by RingCentral App. However, you can use RingCentral API platform to implement such a feature for your service.

Let me know if you have development resource and are interested in building such an app.

This is mostly Contact Center Feature. However, if u could keep track of abandoned or call drop off calls using RC APIs , then you can initiate/schedule outbound calls using Ringout/Callout APIs . Let us know if you need assistance with the logic or dev resources, Phong or I can assist you.