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I've faced same problem but now I have 9.5.4. If you follow these instructions then you can too download it:
1. Go to setting
2. About phone
3. System update
4. Go to menu option or click on 3 dots on top of the screen
5. Select download update
6 Here you go
note: you have to download it 2-3 times then your phone will able to download 9.5.4 os.