My case has now gone to the BBB too.
My issue was quite different to others' cases. For me the discount showed and then when I clicked through to checkout I had been charged the full amount. So my complaint was that they refused to cancel it rather than they cancelled it and refused to honour the booking.
After much back and forth by email, I phoned them. The guy seemed half helpful and told me they would cancel the booking if the hotel agreed to it. He said he would call the hotel and ask them for permission to cancel and if they said yes I could have a refund.
As it happens, I know the hotel very well, and they know me, so I wrote to them myself and said look, I made this booking via Expedia, it was an error and they did not charge me correctly, they are going to be calling to ask if you mind cancelling this booking, and sorry for the bother etc.
I got an email back within the hour along the lines of "Hi Johnny, we have found your booking and it is now cancelled on our reservation system, we are just waiting for Expedia to call and we will confirm that they can refund the money.
All sorted! Or so I thought. Expedia emailed back two days later saying they had spoken to the hotel and they have refused to cancel the booking. So on the one hand I knew the reservation had been cancelled by the hotel, and on the other hand, Expedia has kept my money. They have not spoken to the hotel, they are actually lying. I know that's quite the accusation but I know it to be true.
I cannot see Expedia has won many friends with this debacle. Their email support absolutely sucks, takes up to a week to reply and then it's like a IHG BRG claim, you end up explaining the same thing every two emails because they are incapable of reading the entire case.
I don't want a $100 voucher, I'd rather rivet my testicles to the side of a Colombian bus than book through their site again. I just want my money back that they have effectively stolen from me.