Additional CRM system for my store

I have my own clothing store, and I already have quite a few customers every month, even my operators are very busy and don’t have time to call everyone back. So I found one system called Phonexa that has calls, plus you can also send emails and keep track of the statistics of it all. But I’m not quite sure how it all connects to my WordPress site. Has anyone used a system like this? Have they solved your problems? And how did you connect them to your site?