The IVR script defines which sound files are played to the caller and when, if user input is expected, and what to do with the user input. A new IVR script is required whenever the sequence of events is to be changed. There are some call handling parameters that can be customized without IVR script changes, such as card length, PIN length, number of retries allowed and call cut off warning interval. All languages supported must be syntactically similar to English. The system can default to English by configuration.
Service providers can supply their own prompts in any language they choose.
The prompts are stored in the TFTP server in the format of .AU files. In order to announce the credit available to the caller, the system concatenates a series of smaller prompts to make up the message. The IVR script will look for and play out files with the names specified, in the order specified in the script. In other languages, an appropriate message might not follow this format. In particular, it may not be possible in some languages to assemble larger numbers for indicating time and dollar credit balances in this way.