PennyLuckshoes.com review for Hextom: WhatsApp, SMS & Push

This app was recommended to be by my Shopify representative. The rep said it was free unless I wanted a lot of extra features. I was hesitant to finish the install when the notification on the sidebar said I could be charged up to $180/month. Something to confirm the app can be used for free would be nice. I want to use this for my CYBER Monday deal to promote my discount code on my homepage for shoppers. I still am unsure of how this will work. I entered campaign information, but don't know where to go from here. Application is confusing so far, but I have barely begun.