My boss received his first iPhone bill a few weeks ago, and it was substantially into 4 figures. He's a very heavy phone user, and was previously on a high-end tariff with lots of call minutes included, so when he switched to one of the standard iPhone tariffs: massive bill.
He went back to the store, explained his situation, and the guy in the store called the network and managed to get him onto a business tariff not advertised online, including a data roaming package which I'd never heard of before!
I know this is a different network, but at least it shows the networks can be flexible on plans.