Verizon unlock question

Hey guys,

So I have a friend who has a Verizon iPhone 4S. She moved to China (where we both are), and Verizon said they have unlocked her iPhone. However, when she tries to put a China Mobile sim in her phone she gets the unauthorised carrier message. We have connected her phone to iTunes, and got the same warning message in a pop-up on computer screen.

I have the feeling that VZW told her that it was unlocked, when it is not.

Any help here? Am I missing something obvious?

(Full disclosure, I always buy handsets from manufacturers, and am British, so I have no experience of unlocking from Verizon.)

Thanks guys, any help will be heartily appreciated!