I would like to share my own experience was with OLA cabs amazing. Actually you need not to call and book and again there is no need of waiting for customer care calls.
If once you have booked through your OLA cabs app which is the driver is available near to you by choosing thruogh you OLA cab smart phone, the driver immediatly will call you for pick up.And far prices are really good and reasonable.I was well satified with OLA cabs.