A call is worth a thousand emails.
Highlight your customer care number using callout bubble.
What else?
The call-out template is pretty much customizable. You can edit the look and feel of the callout bubble using custom CSS, change the message to suit your visitor profile, edit the targeting to change whom and when do you want to show this overlay popup.
How? Steps to follow:
Important!! - Refer http://blog.webengage.com/2014/07/09/callout-notifications/ - on how to add element Id for this template
For any help with the integration, drop a mail to: support@webengage.com