It seems that there was a billing problem with one of the apps. They charged me several times the same service.
After getting support from the app by clicking on get support located next to the app name on the Apps settings page; they mentioned I should contact Shopify support and they will process my refund.
As you all know, contacting Shopify support is impossible. I only have this way to know if someone could help me out with this or guide me on how to obtain refunds from apps that are directly billed through Shopify.