According to this handy dandy website, My Sprint Samsung S6 can hit the 2500 LTE band on China Mobile or China Unicom, but Unicom also matches up for UTMS.

https://www.frequencycheck.com/compa...g-zero-f/china

So better compatibility with Unicom, but I've heard China Mobile has the better network.

China Mobile offers this
https://www.hk.chinamobile.com/en/co...ces-china.html

Which offers 1.5GB of 3G/4G service for less money, and appears to route through HK so no GFW. Calls/Texts home over Hangouts/Voice using my US number.

Or I go with the Unicom Data Sim. They have a cheaper 7 day that just does HK/China, but I'm there for just a bit longer, so probably stick with the 30 day SIM. Found one other online user who confirms that google services worked on this card, so should still route through HK. Same plan - Calls/Texts home over Hangouts/Voice using my US number.

http://www.cugstore.com/usa/data-car...0days-1gb.html

I also have boingo wifi access through my Amex, but haven't used in the past.