Originally Posted by
jamar
Unfortunately, the only dual-number SIMs reliably available to purchase in HKIA are China Mobile, landside on the departures level near the south security checkpoint. If your phone supports TD-LTE, great. Otherwise, you get rather slow data.
I'm also bringing back a few CMHK/Unicom HK SIMs with me when I return to Shanghai from HK tomorrow. I know people who will want them in a few months.
(One example: A group of students visiting Shanghai on a short-term exchange, most days planned out with only a few hours free here and there. They'd heard stories from groups coming previously about the rather long lines at China Mobile/Unicom to get SIMs registered. They wanted SIMs with data, but didn't want to waste one of their few free afternoons on getting a SIM. Solution: order CMHK SIMs off Taobao.)
Comments on your post from top to bottom (I don't feel like using multiple quote tags):
1. I would never have guessed that not a single merchant at HKIA had inventory of Unicom HK SIMs, but I defer to you on this point because it seems like you've done your homework
2. I used to swear by Mobile because the signal quality and coverage (e.g. the elevators and basement in my building) are better than Unicom, but I now recommend Unicom for anyone who isn't positive that their phone supports Mobile's LTE standard (many FTers have sent me sad PMs on this topic)
3. I would never buy a SIM at a Unicom or Mobile store
-you actually pay less for them on the street if you're willing to accept a less than optimal number
-buying them on the street takes less than 30 seconds
-you can register at any time (e.g. when you happen to walk past an empty Unicom store)
*registration is completely unnecessary for people who plan on pitching their cards, but for semi frequent visitors, there are a few upsides (e.g. turn off monthly billing)