The same principle applies to online casino payments too. If you purchase something with your phone, you can add the price of that service/goods to your bill and pay it in installments.
You pay a bill each month to your carrier. The idea is simple: You have a mobile phone. Paying with a phone bill is actually a common method: You may already have done this in the past to purchase some goods or online service.
Alright, we can start explaining the logic behind online casino mobile payment system.