Usually if the game is malfunctioning, all pays are void. With your description I'm sure that's what happened , since you logged out and in to confirm.
Maybe cause between the time they sent euro, and bank/visa converted it to nok the currency had a change?
Also if visa does the currency exchange, and not the bank its usually more expensive.
Thats great, people sometimes do mistakes and this guy let you know asap. If he tried to hide it id understand, but he was open. Happy to hear you guys will try to fix it the best way possible:)
I disagree with casino here, since you let them know before you did anything. As i see two options, reset balance and wager till before you bought bonus, or just give you the loss of 800 kr and cancel the bonus feature in money train. I assume both solutions are better then current?