How how how can that be??!! This is the year 2016, and I can’t set basic options like the number of rings! Actually I too want to turn off voicemail completely. I am aghast to read I don’t have a choice.
Phone Call Recorder - ACR is "free." It trumpets that all call recordings, incoming or outgoing, even photo calls—meaning FaceTime calls—are unlimited in length. But that's if you upgrade via in-app purchase to the pro version for $59.99.

ObjectiveApplies ToProcedureChange Voicemail Settings in Account ManagerAdditional Information ObjectiveApplies ToProcedureChange Voicemail Settings in Account ManagerAdditional Information Please note: there is no default voicemail password. If you have forgotten your password, you can reconfigure it in your 8x8 Work application, or contact your system administrator. Note: Setting up voicemail for a Toll-Free Number or Virtual Number (such as your main company number) simply depends on what extension the number is pointing to. After that is established, you can proceed to set up voicemail for that extension using the steps provided below.
The importance of voicemail in the customer care sector has not diminished despite the arrival of newer web technologies. VoIP applications let the businesses use voicemail service with flexibility, as it is. The users need not rely on extension terminals when they use VoIP services. A strong internet connection is a prerequisite and the pre-configured phones can be used – both for calling /receiving calls and for automated custom greetings. IVR feature redirect callers to the right virtual extension where their needs can be addressed. This can be done anywhere through a web portal access and an internet connection.