You can downgrade by yourself.
1. Install december 2017 OTA from sd card.
2. Then install full firmware 7.1.1 june 2017.
3. Install OTA 07.17 => 08.17 => 09.17 => 10.17 => 11.17 => 12.17 from sd card
4. Turn off updates in developer settings.
After all you get 7.1.2 with last security updates.
Sorry, i can't provide more information on actually HOW_TO_DO_THIS_TRICK.
If you are doing this, you should be fully adapted for that diffucult process and have to read much information and guides.
In short, if you really need this, all you should know, that this is possible and information about this process you can find somewhere around www.
Thanks. There is no service center in my country and downgrading by myself seems a rather dangerous activity in it self. dont want to kill my phone completely