Confused by T-Mobile's Abroad rates

[PureAppleJuice]

Basically i'm going to New Zealand in a week tomorrow - I'm on the FlexT 20 package. Obviously the calls are much more expensive, but not as pricey as I thought they would be. I was wondering if they'd just add those calls to my bill, or take it out of my allowance, but more of my allowance takes a hit.
Also any idea how much it would cost to call from new zealand to spain with t-mobile?

Thanks,

 

[PureAppleJuice]

Thanks for the replies. Would seem you're right, had to read all the crummy little small print. Calling cards it is ;D