The user in this situation is billed after the fact according to their use of mobile services at the end of each month.
Typically, the customer's contract specifies a limit or "allowance" of minutes, text messages etc., and the customer will be billed at a flat rate for any usage equal to or less than that allowance.
Theoretically, a user in this situation has no limit on use of mobile services and, as a consequence, unlimited credit.
In the US a smaller market has been captured by prepaid providers such as Boost Mobile, Metro by T-Mobile, Cricket Wireless, TracFone, and Ting, which use postpaid providers networks (e.g. Cricket runs on AT&T's network).
The alternative billing method is a prepaid mobile phone, where a user pays in advance for credit that is then consumed by use of the mobile phone service.This article related to telecommunications is a stub.