I cannot ubdate software
I want to use my mobile with piece
iPhone 6 Plus, iOS 12
Please follow the steps at Update your iPhone, iPad or iPod touch – Apple Support to update your iPhone.
As you are using an iPhone 6 Plus, you are unable to get the latest version of IOS, the latest update available to you is iOS 12.5.5. Sadly you will be unable to upgrade past iOS 12.x
If you are still struggling to update your device please follow the steps at If your iPhone, iPad or iPod touch won’t update – Apple Support (UK)
If I have misunderstood your issue or can be of any further assistance, please let me know.