If you add a specific ringtone to a contact, you'll easily identify the caller when the ring goes off. To assign a ringtone to a contact on Galaxy S7 (Edge), do as follows:
1. Open the Contacts app on your Galaxy device
2. In the list of your already added contacts, tap the one you want to edit and assign a new ringtone to
3. Tap the Edit button (It's located on the right corner of the screen, next to the More button)
4. Now scroll all the way down and tap the More button
5. Scroll again, until you see the Ringtone option.
6. Tap on the Ringtone and select the new ringtone from the list
7. Hit the Save button and the new ringtone will be assigned to that contact.