Inputting numbers on the app and grouping the callers together is 10x easier on the desktop app than it is on the phone. Most people choose to add the information in on there so that they can see it when away from their desk. When somebody leaves a voicemail, the phone system knows who it is from and will say the person's name i.e. "Message received from 'Jane Doe'" and continue on however, you can't see that information on the main screen on the phone when the call is coming in. Having to input the number more than once is a hassle and time consuming for the parties who are in charge of those tasks, also, why should you have to repeat work that has already been done once? This would save time and make it easier for all parties if the app could fully integrate the information that the user puts in to the physical phone.