It is very easy to disable Call phone option in chat list of Gmail. You can follow given steps to disable ‘call phone’ feature:
1. Simply click gear icon at Gmail’s upper right corner and then you can click on Mail settings.
2. Under mail setting click on Chat tab.
3. Now click Disable outbound voice calling under the section of Call Phone.
4. Now you can save the settings by clicking on Save Changes.
Following given setting will disable only Gmail’s outbound calling. Those who have allowed forwarding calls in Google voice Chat, they will have to disable those settings independently.