That sucks, and that's CRAZY that they have that amount preselected like that! I had to get on the phone with DoorDash earlier, because I was removing one of my payment methods, and then the next screen it took me to had the thing about signing up for the DashPass subscription (Where you're charged $9.99/month). I wound up accidentally tapping the button to 'accept', and so I immediately cancelled the subscription and called them asap to make sure it doesn't go through.
I think all of these sites (and apps) should have a confirmation message that asks "Are you sure you would like to purchase _____?" That way, you can easily get out of it if you clicked it by mistake.