Germans Doesn't Like iPhone VoIP

In Germany, the T-Mobile, a big multinational company related to mobile network, seems have some annoyance for the use of VoIP over the iPhone, precisely with the service offered by SipGate, because it encourage operations named "jailbreak" (a description of this procedure it's available in this page), and then tamper the iPhone via software.
I have the feeling that the cheap VoIP begins to make some trouble to the big multinationals, that certainly will take some measures to protect themselves, even if more than a measure, it seems an egoistic monopoly.