Reading further down the Twitter conversation it sounds like if you don't buy your iPhone outright from the Apple Store it'll lock to the first carrier you try to connect it to. The lady on Twitter was pissed because she had a unlocked phone, put an EE pay-as-you-go SIM in it on a 30 day contract, only to find EE had locked her iPhone to EE, and wouldn't unlock for 6 months.

What's going on, is it appears as though someone is accusing EE of carrier-locking an unlocked iPhone when an EE sim card was put in the phone. If this is the case, I would expect if the UK has customer protection laws, that EE would get a mild slap on the wrist.

The linked Twitter conversation is probably more informative. https://twitter.com/didlix/status/522086210383405056/photo/1 Looks like EE locked her phone to their carrier when she inserted the SIM into her previously-unlocked phone.

EE's only response is to link to this page http://ee.co.uk/help/getting-started/joining-ee/unlocking-yo... which says that phones cannot be unlocked in less than 6 months.

It looks like car phone warehouse supplied her with a locked phone to EE, and not a unlocked one she thinks they sold her.