I while ago I bought something by mail order, didn't work so I sent it back. I paid by credit card and it cost me £25. When I sent it back I was told the amount would be refunded to my credit card.
When I got my statement they had actually refunded £250.00 instead of £25.00 but the day after they charged £225.00 to my credit card, obviously someone had put a 0 too many and had charged the difference the next day when they noticed.
I've been refunded what I'm owed so there is no problem but out of interest what would happen if I disputed the £225.00 charge with my bank? I'm not going to try it but I'd be interested to know what would happen.