Don't think 7/11 will do any unlocking. Best thing is to take it to Mongkok on Argyle street opposite Ladies Market (sorry not that kind of ladies market which is kind of ironic on this website!!). That place (I think the name is Shintak center or something like that) is the best place in HK to unlock, buy, sell, rebuild, find missing parts etc... for your phone.
And while you're waiting you can go right across the road on Sai Yeung Choi street for a quick punt while you wait!!!