ios 12.4.9 is not displayed on my iphone software update

I'm guessing that you do not wish to answer my question? What is the current software on the iPhone? Then what happens when you go to Settings>General>Software Update? Have you tried to update over the air?

See this: Update your iPhone, iPad, or iPod touch - Apple Support and this:

If you are not seeing iOS 12.4.9 as an option, are you sure you have an iPhone 5s? If you go to Settings>General>About>Model Name or Model Number, what do you see there?

Then you need to use the instructions provided in my last post to try and update to iOS 12.4.9, either over the air or with iTunes.

It is the response just above your last one. The one I sent with the Apple Support link, and the YouTube video.