There is a mock credit card authorization program available for your use.
This program will not accept real credit card numbers (it actually does the credt card check digit calculation and rejects numbers that pass). It will also reject credit card numbers that are less than 14 digits long.
The available balance is determined by the 3 digits after the bank identifier (which is 6 digits long). Those 3 digits are multiplied by 100 to determine the available balance.
Program call markup language, which contains the program name and parameter information, can be generated when an i5/OS program is compiled. The ZEND Core functionality on i5/OS can use this PCML to prepare a program call.
The PCML for the CCAUTH program is available here.
There is an example page using this program here.