I have currently been selected to be the voice of a well known major financial institution for their answering service and on hold information. My voice was chosen unanimously from a wide variety of candidates that auditioned for this opportunity.
I also do daily telephone escalations for a company as a stress reducer for their customers before handing the call off to a resolution coordinator.
Training has been all through experience and trials. I put myself in situations that create the need for public speaking and areas in which different tones and voice characters help to "manipulate" or "sell", if you will, the business need.
I've worked with the public on numerous occassions. I've also read children's books, creating exciting and mysterious characters, for classrooms of school-aged children.
I've used different voice persuasions for sales, training, and customer service.