be weary of the advance check out during overnight promo, they will nail you with a full charge

I checked out my car 6 min early during the over night promo of half off, and they charged me for the whole day saying it is a strict policy. i've been renting for months now, always check out early, always check in on time, never a problem, after an hour with customer service, they wouldn't do anything to alleviate my frustrations. APPALLING...i want my $50 back! jerks.