I am using xiaomi redmi 1s. In every 15-30 mins, my phone pings something by mobile data. Even the mobile mobile data is off and I am using wifi.This leds to plenty of usage display messages by the operator. Sometimes i need to reinstall the battery to refresh and avoid these messages.(phone gets stuck by the messages).Currently am using mokee MK4.4 armani release, but the same problem comes with stock MI rom also.
I was having the same problem, had mobile data off and still it kept on charging 4 paisa now and then. Eventually I seem to have resolved the issue by checking "restrict background data" in advanced settings of mobile data.
I figured out that in my case the location was enabled which was accessing mobile data. To see what is causing your data to leak, you can install mobiwol from play store and it would display the applications which are accessing mobile data and wifi.