Apple expected to discontinue iPhone 13, 14, 15 models ahead of iPhone 16 release EARBORN

You can see what models of iPhone Apple is still selling here:

iPhone - Apple

The iPhone 13 is discontinued as are the iPhone 14 Pro and the iPhone 15 Pro. You may still find some of those models at Apple dealers or in Apple's refurbished models.

What is, or isn't available has already been updated.

The 13 is gone. The 14 and 15 are only available in the standard models. The Pro versions are gone.