Booked a ticket in either V or H, and finished everything, paid... Then, when I went to check the reservation again, it listed me in D and let me choose seats up front! I asked Continental about this, and they said I owe them $3000

The rep told me that someone changed the reservation, but I still need to pay the difference in fare and the penalty (even though apparently this change was made within 24 hours)...how could CO bump me up to BF w/o first making sure payment went through?!?! AND WHO BUMPED ME!!