How to unlock an iPhone: How much should I pay to unlock my iPhone?

Ideally you shouldn't pay anything to unlock your iPhone, because your carrier should unlock it for you for free. But some carriers are making admin charges of around £20. Third-party companies seem to charge between £10 and £25 to unlock an iPhone, and we wouldn't pay over £25 to unlock an iPhone. Shop around if anybody quotes you a higher price than that.