CrestaProject

<a href="https://crestaproject.com/cresta-help-chat-demo-page/" rel="nofollow ugc">Plugin Demo</a> | <a href="https://crestaproject.com/downloads/cresta-help-chat/" rel="nofollow ugc">Plugin Homepage</a>
With Cresta Help Chat you can allow your users or customers to contact you via WhatsApp simply by clicking on a button. Users may contact you directly in private messages on your WhatsApp number and continue the conversation on WhatsApp web or WhatsApp application (from mobile). 
You can use the floating button which is positioned at the bottom right of the site or a button inside post or pages using the [cresta-help-chat text=”Need Help?” icon=”yes” position=”top”] shortcode. 
Cresta WhatsApp Chat is compatible with WooCommerce and WPML.
Some features
<ul>
<li>Add the button to open WhatsApp Chat at bottom right of your site</li>
<li>Use the shortcode [cresta-help-chat] to add the WhatsApp button in your posts, pages or custom post type</li>
<li>Choose which pages to show the WhatsApp Chat button</li>
<li>Mobile version: click the button and automatically open the WhatsApp App (if installed)</li>
<li>and more…</li>
</ul>
PRO version features
<ul>
<li>Change position of the box button</li>
<li>Change colors of the box button</li>
<li>Add tooltip on the box button</li>
<li>Change box size</li>
<li>WhatsApp widget</li>
<li>Different Animations</li>
<li>and much more…</li>
</ul>

Cresta Help Chat

Allow your users and customers to contact you via WhatsApp with a single click.

zendesk_official

Zendesk Support for WordPress allows you to bring your helpdesk, powered by Zendesk, into your blog or site. Here’s an overview of all the features:
<ul>
<li>
Single sign on with Zendesk’s Remote Authentication 
Have a healthy user base already? With Single Sign On, your users won’t have to login to Zendesk Support to submit tickets, check their progress or comment in community forums.
When users try to login to Zendesk, we’ll ping your WordPress site to see if they’re already logged in, and then sign them straight into Zendesk without them needing to register or set a new password. It’s 100% secure, too!
</li>
<li>
Turn your blog comments straight into Zendesk Support tickets, with one click 
Need to take that conversation offline, or escalate someones question or problem to someone else in the company. From the comments administration screen, you can take any comment made and turn it into a Ticket. The process is completely seamless for your users, and they’ll appreciate the extra mile you’re going to provide amazing customer service.
</li>
<li>
The Zendesk Support Web Widget 
Add the Zendesk Support Web Widget to any webpage so users can search your knowledge base, chat with an agent or submit a ticket. You can have it on every page on your WordPress blog, or choose where you want it with the use of a template tag.
</li>
<li>
The Zendesk Support Feedback Tab 
Add a tab to any webpage so users can search your knowledge base, chat with an agent or submit a ticket. You can completely customize the look and feel. You can have it on every page on your WordPress blog, or choose where you want it with the use of a template tag.
</li>
</ul>
Note: Zendesk Support Dropbox users – the dropbox (also known as Zendesk Support Feedback Tab) is soon to be deprecated and has been replaced with the Web Widget. You can continue to use your dropbox for now but we encourage you to try the Web Widget (available in your plug-in) which allows you to easily embed ticketing, self-service and chat on your website as well as providing a much improved experience on mobile web browsers.
<ul>
<li>
Access your tickets from your dashboard 
Full access to your views, tickets (including custom fields) and comments. Never lose sight on your support requests, no matter where you are.
</li>
<li>
A simple contact form, on the dashboard 
Give your visitors the ability to quickly submit a question or issue with a two field contact form. You can place this on the dashboard, restricting it to only those with Zendesk accounts, or you can allow anyone to open a request regardless of a Zendesk account.
</li>
</ul>
Like the sound of this plugin but don’t have a Zendesk account yet? Sign up in just 30 seconds for a 30 day free <a href="http://www.zendesk.com/?utm_source=wp&utm_medium=dl&utm_campaign=wppin" title="Zendesk help desk software" rel="nofollow ugc">help desk software</a> trial with no credit card needed.
<h3>Publishing a new version of the plugin on wordpress.org</h3>
If you are a developer looking to release a new version of the plugin 
See: https://zendesk.atlassian.net/wiki/display/ENG/Publishing+new+versions+of+plugins+to+Wordpress.org

Cresta Help Chat vs Zendesk Support for WordPress