Is yours a mobile company card? If it is mobile, go to the mobile hall and open it.
If it is Unicom, go to Unicom to open it.
It's the same if you want to turn it off. (Actually, you don't have to turn it off. You don't have to pay for making international calls. )
You can call Hong Kong after opening. (00852+ phone number) is the same as sending a message. 00852+ mobile phone number.