http://stackoverflow.com/questions/3644144/how-to-disable-mobile-data-on-android

The Dataconnection disable and enabling APIS are hidden in the SDK and not exposed to the user, this can be achived by accessing the ITelephony interface using the java reflection technique.

here you go:

    Method dataConnSwitchmethod;
    Class telephonyManagerClass;
    Object ITelephonyStub;
    Class ITelephonyClass;

    TelephonyManager telephonyManager = (TelephonyManager) context
            .getSystemService(Context.TELEPHONY_SERVICE);

    if(telephonyManager.getDataState() == TelephonyManager.DATA_CONNECTED){
        isEnabled = true;
    }else{
        isEnabled = false;  
    }   

    telephonyManagerClass = Class.forName(telephonyManager.getClass().getName());
    Method getITelephonyMethod = telephonyManagerClass.getDeclaredMethod("getITelephony");
    getITelephonyMethod.setAccessible(true);
    ITelephonyStub = getITelephonyMethod.invoke(telephonyManager);
    ITelephonyClass = Class.forName(ITelephonyStub.getClass().getName());

    if (isEnabled) {
        dataConnSwitchmethod = ITelephonyClass
                .getDeclaredMethod("disableDataConnectivity");
    } else {
        dataConnSwitchmethod = ITelephonyClass
                .getDeclaredMethod("enableDataConnectivity");   
    }
    dataConnSwitchmethod.setAccessible(true);
    dataConnSwitchmethod.invoke(ITelephonyStub);