A ringback tone service may be configured by determining an indication to suggest one or more callers to a user of a mobile-telephony device and obtaining historical call data describing recent calls placed by recent callers to the mobile-telephony device in a recent period of time. After identifying a number of frequent callers for whom no custom ringback tone is currently provisioned, the user is prompted to select from a list of custom ringback tones that are available to provision for incoming calls from the frequent caller(s). In some cases, the user may send a message to the caller, allowing the caller to select his or her own custom ringback tone via a user interface provided by a ringback tone-service provider.