Got a GSM phone? Check out this page for some information on some cool GSM stuff. Wondering if you have a GSM phone? In California if you're a T-Mobile or Cingular customer, you are using GSM. T-Mobile, in California, runs on Cingular's network (In New York, Cingular GSM runs on T-Mobile's network). If you run MetroPCS in the Sacramento or San Francisco Bay Area you're CDMA (running on SprintPCS's network) Nationwide, if you're a T-Mobile user, you're GSM. If you're AT&T or Cingular you can be either GSM or TDMA. If you're SprintPCS or Verizon, you're CDMA.