Why does my phone store all its data in the internal memory.

[AC Question]

I have a Morcomax a106 it has three different types of storage internal storage, phone storage and sdcard storage. And all system files, any apps i download gets stored in the internal storage which only has 1gb of space, even if i change the default write disk to sd card. I've tried a lot of things, even resetting the phone! but this problem is not disappearing, please help.