How do I use the Phone Calls module in Vtiger CRM?

To use the Phone Calls module, you must first install it from the Extension Store. You can access the Extension Store if you are an Admin user. 
Follow these steps to install Phone Calls:

1. Log in to your CRM account.
2. Click the User Menu on the top right corner of the screen.
3. Click Settings. 
4. Look for the Extensions section.
5. Click Add-ons.
6. Look for Phone Calls using the search bar.
7. Click Install.

After you install the module, you can see it under Main Menu > Essentials > Conversations.