Cingular Maritime and United Mobile?

[kupe]

Hey gang-

We will be cruising aboard a Celebrity ship later this year in Chile and Argentina. They claim to have "Cingular Wireless Maritime Service" aboard. This is what they say:

Cingular Wireless Maritime Service will be available for use when the ship is in international waters. When you are at sea, you will know you can use Cingular Wireless Maritime Service when your mobile display indicates that you are roaming on "AT&T Wireless". Charges will be conveniently billed to you by your home network.

For questions about your service or about billing, please contact your home network customer service.

So, my question is, when using this service with a United Mobile phone, what rate would apply? Would UM see this as a call originating in the US and bill accordingly (ouch!). Or would some other rate apply? I've seen threads with outrageous fees for Maritime service, but how would they apply that to a prepaid like UM? For that matter, would a UM phone even be able to roam on that network? Anyone tried this service?

Thanks!

Kupe