Travel Technology - Intl roaming and GPRS with Simplus/Optus outside Australia

Hi
Does anybody know how SimPlus / Optus charge for International GPRS?

I live in the US and use my optus sim for International Roaming. Since Ive
got my PDA, there has never been a data section on the bill.

The only thing Im getting charged for are these weird 999000000XX (XX is
another 2 numbers) and a min/sec.
Which I presume, the prefex 999 refers to GPRS. and the XX are the seconds.

The rate looks like 0.43c connect rate and then 1c per second.

Ive emailed simplus a few times and they are saying this is the charge to
connect to the local network for GPRS, then they charge their Optus Zoo
amount for the kb download.(Which I never been billed)

There is nothing in their price list that says there is a per minute network
charge to use GPRS on an oversea's network. Unlike SMS and MMS, which
clearly says the additional charges.

Question is, has anybody come accross this, and can share some light?
Im thinking that this is actually the kb download but they are charging it
as a min/sec instead..

--
Robert