Many websites list this phone compatible with the Volume UP + Power button combination. However, I have seen that with the latest updates to the firmware, this operation isn't possible anymore. You will have to use a 3rd party hardware box that's capable of accessing the internal memory of the phone. You can install the app on your computer, but the phone needs to be connected to the box in order to access the memory to format it. VIsit a local phone shop and they will format the user_data from your phone (also called Factory Reset).