Twilio Easy Call is a WordPress plugin enables your company to convert web traffic into direct communication over the phone, with just the click of a button.
This plugin integrated with TWILIO (Cloud communications platform for building Voice & Messaging applications) http://www.twilio.com
To use this plugin you should have paid account on Twilio to be able to enjoy with the voice service
Please see Twilio Pricing here https://www.twilio.com/voice/pricing
