iOS 13 is this update for all iphones now, my phone is telling me my software is up to date but it is only 12.4.3

Which model do you have?

iOS 13 requires an iPhone 6s or newer.

Sorry. Your phone does not support iOS 13.

If your iPhone has 12.4.3, then your iPhone is an iPhone 6 (Plus) or older, those cannot support iOS 13.

12.4.2 and 12.4.3 were only released for devices incapable of running iOS 13.

See: https://support.apple.com/en-us/HT210327