Advantage 
           (1) Data service will be activated within 24 hours. No need to wait till next month
           (2) You can deactivate the data service when you leave china
           (3) Cheapest way to get CMNET data service.


I'm using iPhone 3GS on AT&T Service in USA. I've tested with iPhone 2G also. 

STEP 1. Unlock iPhone
               You may can find so many unlock guide, so, I don't want to rewrite. 
               I recommend to use Dev Team's Jailbreak & Unlock

STEP 2. Buy Pre-paid SIM Card
               You must buy 'M-Zone' simcard, I have bought at local phone store by 75 yuan ( around $13 USD)
               When I check the balance, it has 36 yuan already. and It support 130 text messages.
               But, I feel it is too small to use ^^

STEP 3. Re-charge
               I have recharge 100 yuan. Just ask  100 yuan recharge card.
               They will recharge immediatly.
               or you can recharge by your self
               (1) call '13800138000' and presss ''2' for english
               (2) select '1' for recharge
               (3) if remove the silver cover on re-charge card, you will find the passcode. enter this number.

STEP 4. Activate GPRS
               it is simple, call '10086'  and select '3' for english and '0' for operator.
               you can ask to activate GPRS and ask 20 yuan / month service ( 300MB/mo, 1 yuan / MB overage, 15 hours media stream).
               This service will applied immediately. 
               or your can send SMS to 10086 to activate this service and deactivate. 

               Send 'BLWHT' to 10086 : Activate Service
               Send 'QXWHT' to 10086 : Deactivate Service

               step_01.jpg 

               Just send 'BLWHT' to activate the service 

                step_02.jpg d

                if you check the account, 10 yuan has been deducted for GPRS service.

STEP 5. 
               Go to Settings->General->Networks->CellularDataNetwork 
               Input 'CMNET' on APN.
               and you may nee to reboot iPhone

                IMG_0044.jpg 

STEP 6. 
              Enjoy.