Most smart phones work perfectly fine in China regardless if they are IOS or Android.
Usually it is just a matter of getting a new phone plan/Chinese SIM card and then popping out your old SIM and putting in the new one.
When it comes to phone usage plans China is almost always cheaper, especially when compared to any international plan.
Usually everyone is surprised just how cheap the data/phone plans are in China.
Make sure your phone is unlocked. If your phone is locked, then you cannot use a Chinese SIM (so either need to get a new phone or have to take care of getting your phone unlocked from here which can be more difficult). Apple users seems to be able to use their unlocked phones much easier. Android users sometimes find it easiest to buy a new phone in China (you can get a half decent one for around 120 USD).
For the arrival process, usually the wifi for your apartment and the Chinese SIM card come as a package. Some teachers are able to arrive and get straight into an apartment.
Especially if you are training in a different area then where you will live you may want to arrive with a temporary SIM. Here is an option: https://www.simoptions.com/prepaid-sim-card-china/
Sometimes it is also possible to get an overseas package added to your current phone plan as well that you can use until you get the new China SIM.
If it is not too expensive, we suggest getting international coverage for a few days or a temporary card if possible from your home country. It is a piece of mind to have wifi while traveling and arriving.