How to update iPhone 6

Hello ~You will need a newer device as your device can’t be updated further.Go to upper left and click on two lines and then iPhone to see your new choices. If you consider a second hand device please take a moment to read these:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone * lobsterghost1 *

~Katana-San~

While you seem to have quickly solved your tech support issue, you will find that an iPhone 6 can not be updated to iOS 13 or higher.