Not sure what a DCC is, but....
I had a coupon for $5 on a rental once, that was not taken off the balance. I e-mailed 3 times, each time being told it would be taken care of. I waited a month, and it wasnt dealt with, so I disputed the amount. Only $5, but it is the idea of it that pissed me off. The $5 dispute went through fine, and I received a hand written apology letter from a manager at that particular Avis, along with a $25 coupon for future use.