SalezTalk provides a simple button to receive call request from your website visitors.
It increase conversions on your website by anywhere from 50 to 500%.
There is a WordPress plugin too.
Intercom Conversations 3.0
Access all your Intercom conversations and customers
Intercom is the first to bring messaging products for sales, marketing & customer service to one platform, helping businesses avoid the stiff, spammy status quo and have real conversations that build real connections.Intercom lets you talk to consumers almost anywhere: inside your app, on your website, across social media and via email.