With the rise of online gaming in the mobile industry, it has necessitated the need for mobile-specific payment processors where previously banking options have been rather limited. There are a number of pay by phone companies across the world (barring the US), the most popular of which are Boku and Zimpler. These companies allow you to make online payments that will then be directly deducted from your cell phone bill.
The basics for the different pay by phone firms work the same. It usually involves activating settings on your phone to facilitate mobile payments first, then you are able to use your phone as a funding method. All deposits made will appear on your mobile phone bill, and depending on the cycle you are in, the transactions might not appear on the immediate bill, but the one to follow. This service is also available to pre-paid users, with the condition that the necessary credit is available upfront otherwise the transaction will be declined.