There are two carriers in Chengdu that I know of. One is China mobile, then other is China Unicom. Apparently, China Unicom is the better choice because the reception is supposed to be more stable and available through the city. Not sure if this is true though cause I just use Unicom, but it’s fine usually. You can buy the sim card in one of Unicom’s offices or in one of the computer malls or in many other places that cell phone services. I paid 440 for 6 months which is about 73 kuai a month for up to 1 gig of service. Maybe able to get it cheaper, but I’m not sure about this. Probably a good idea to check around one of the computer malls and see If you can maybe get a special price.