Bulibasha review for SL: WhatsApp Chat + Marketing

Hi guys, I just start using it this app, and loving it. I will see results after sending messages for abandoned chek outs to my costumers. However- I cant reach out to you by email, seems like something is not working, so I need to ask here, what does means charges per usage 300$ may apply? What usage is this refering to? Loooking forward to hearing from you. Thank you