The one irreversible mistake
Sending the right coin on the wrong network puts your money in an address that exists on a chain we are not watching. Nobody can move it back — not us, not the exchange, not the wallet vendor.
So the payment screen shows the network in words, not just an icon, and refuses to be subtle about it. Read that line before you paste the address anywhere.
Everything else is recoverable. Sent too little? Top it up. Sent too much, or too late? We pay the difference back.