Please tell us some basic information before asking for help:
Model Name: ZF9
Firmware Version: Latest German one
Rooted or not: NO
Frequency of Occurrence: Every time
APP Name & APP Version (If your issue relates to the app): Call Interface
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When I am in a call and just hold the device to my skin, the phone gets back but is still being used like normal. I was wondering what was going on when having it vibrating all the time but the phone don't really lock itself. It just works like "normal" so you always have to lock the phone with its power button before putting it to your skin.