Ios update

iPhone 6 can only be updated as far as iOS 12.5.7. It is practically obsolete at this point and will not run many apps.

If you want to run iOS 15, you need an iPhone 7

If you want to run iOS 16, you need an iPhone 8

The bottom line......you need a new phone.

If you look at the chart I posted in my previous reply, you'll discover that an iPhone 6Plus model cannot support more recent iOS versions beyond 12.5.7, sorry.

Regards

Giulio

If your unidentified iPhone model is still running the prehistoric iOS 12 version, most likely it cannot support more recent versions. See why in this compatibility list:

Enock