No matter whether your plan is credits roll over or incoming messages are free, voice message costs are the same.
No matter whether you are on the rollover or incoming free plan for SMS, the price for outgoing voice messages is the same. At the moment, that is 2 credits/min to send a voice broadcast or make an outgoing call.
Incoming calls cost 2 credits per minute, if you are not using the call forwarding feature. If you are using the call forwarding feature, incoming calls cost 3 credits per minute. If your caller leaves a voicemail, it costs 1 additional credit, and if the message is transcribed, it costs an additional 4 credits.
If you are looking for directions on how to send a voice broadcast:
Using V3? This is the article for you.
Using V2? Check out this article HERE.