[user5994461]

Bank transfers between banks are not reversible.

[netsharc]

Do you mean when the mortal clients of the banks are doing them, or when the banks are doing them?

I imagine bank CEOs know each other and can even call each other and say "Oh sorry old chap, that was a mistake!".

[zuppy]

you are reading an article about a case when the bank could not take back its money, I think this answers your question :)

[sukilot]

That's because the recipient didn't want to return it.