£13.30 is the correct fare for this journey as you used the Elizabeth Line to get there.
£5.60 is the fare if you’d used the underground all the way and swapped to the Picadilly Line on your journey.
A good way to save more money on this trip would have been to get the Picadilly Line and split your journey at Hatton Cross – tap out and then come straight back in again.
As Hatton Cross is in the Heathrow Free travel zone so you would avoid the Heathrow premium and pay nothing for your trip from Hatton Cross to the terminals.
So sadly, you’ve not been overcharged but remember that the £13.30 counts towards the daily cap so if you’re making a return trip you won’t pay more than £14.90 for the day.