I am unable to update iOS on my iPhone 6s

“doesn’t have the software update option “

And it won't, if this is an iPhone 6 and iOS 12.5.7 is already installed, as I suspect is the case.

Read carefully and you will see that so far, the OP has told us that he has an iPhone 6 and an iPhone 6s. Take your pick.

sberman is assuming it's an iPhone 6 based on the other information in the post. I am as well. We may be wrong.

We won't know until the OP posts back to clarify.

If you have an iPhone 6S as indicated by the footer here and not an iPhone 6 as indicated in your posting, then that iPhone 6S can get to iOS 15.

The usual update procedure:

• Update your iPhone or iPad - Apple Support

What to do:

• If your iPhone or iPad won't update - Apple Support

You will need a Wi-Fi connection, and cannot update (directly) using cellular. Or you can use a Mac or PC to update.

If you have Screen Time or Parental Controls enabled (IIRC, Focus isn’t available as far back as iOS 13), turn that off and check again.

If this iPhone is managed or supervised by an IT organization, check with IT for assistance.

If you can’t see the option software update in your iPhone settings then you have to use Apple devices app on windows 10 or 11 or if you have a Mac you can use finder but remember your iPhone it’s compatible with iOS 12.5.7 only

Update software on your iPhone, iPad, or iPod touch - Apple Support (CA)

The iPhone 6, released by Apple just short of ten years ago, cannot be updated beyond iOS 12.5.X.

Did you read this before reply ?

“doesn’t have the software update option “