Just like a cell phone, you most likely need the "unlock code" so that you can allow access to use the HK Sim card. I would suggest you contact the company you bought the phone froma nd ask them for the unlock code
I have been using them for years now and you cannot simply put in a sim card here, you need to pay for the privelege.
When I asked if you have roaming, do you? If so, you can use your UK sim card here.
You can try Smartone and Csl1010 and ask if they will allow you to have a short term policy.
Tidings2... Why in the world would sombody want to "roam" witha cellphone here and pay the very high roaming charges. In Most cells phones, you cannot use any other sin card without an getting and using the manufacturer set unlock code thay allows you to use other countries sim cards.