When you contact a customer through the phone, what is the most important element that affect the communication, Verbal, Vocal or Visual?

Thanks for invitation. Verbal attributes of the conversation are the most important followed by Vocal. It is all in the delivery of the message and response over the phone so it you don't use your voice properly the message you are sending may not be what you intend. 

They will visualise you - so how you project yourself is key but not the most important element of the call. 

The most important affecting communication and verbal element is to have my voice much better than visible .. but in the case to view or inform the customer what the product will be visible here with voice ..