How to update my iPhone (iOS 12.5.5) (6Splus) to iOS 13

iOS 13 is not available as an update anymore. iOS versions 14/15 are.

Are you having difficulty updating your iPhone past iOS 12.5.5? One thing that you should know and confirm and that is whether you have an iPhone 6s or do you have an iPhone 6 (Without the S) This is important because an iPhone 6 can only be updated up to iOS 12.5.5 and NOTHING HIGHER. You need an iPhone 6s to update higher than that to iOS 14/15. Double check which iPhone you have.

Open Settings ➔ General ➔ About ➔ Model Name: What does it state there?

Axel F.

If your software version is 12.5.5, you have an iPhone 6 Plus, not a 6s Plus. A 6s Plus would never have had the opportunity to use that version of iOS