Configure Payment gateway Zombaio on modenacam

Hello I have installed Zombaio payment gateway on my website. Everything works fine but now I want the available credits of the user account increase on my website when the payment is made. The form is already configured on my website. When the user click on submit, he is redirected to the Zombaio page where he pays using his credit card. After the payment, Zombaio redirect him back on my website but the user credits still 0. I want the available credit of the user account to increase when the payment is ok. It is an quick easy job. The script of my website is called modenacam. You must be familiar with Codeigniter.