Right, if re-entering the card details was unrelated to accidentally hitting the freeze button then it’s definitely less of an issue than I first thought.
In that context your points about making the freeze card button in the prime position seem valid, but that does still come at a cost to the most common action.
I’m speculating now, but perhaps the page could do with a UX pass to give it more structure? Right now the page is a little unstructured; you’ve got your balance, then “Top Up” presented in a way that at first glance seems like a title, then the big card image which doesn’t serve much purpose other than (I guess) to confirm to you which card you’re topping up (can you have more than one? Does anyone read the numbers and confirm? Could it be ditched?)
More speculation but I’d also wonder whether the position and style of the freeze card button would actually help someone in a panic. The reason I keep (nearly) hitting it is due to its location under the thumb. Because the page is lodged in my brain as “the top up page” then autopilot kicks in and I push the most accessible button. If I was in a panic would I be so ready to hit buttons, especially since I wasn’t in “top up” mode, and would the subtle contrast of that button stop me seeing it?
More questions than answers, sorry!