@Shane172 I suggest you contact them through Twitter, which is said to get the best and quickest results. Airbnb is known for not ever calling back, even though they tell you they will. And I usually get decent results by contacting them through messaging as well- you have to be extremely clear with them what the issue is, or, like you found, they don't seem to understand.
Like this:
"I was trying to book xx for xx dates.
I got an error message that the place was unavailable for those dates.
So I booked the place for the following weekend INSTEAD.
Now I see that I was charged for the first reservation dates, which I was told were unavailable, as well as being charged for the second reservation.
I only wanted one booking.
I need to you to cancel and be refunded for the first booking I tried to make, as I was told the dates were not available.
Thank you for your assistance."
Short concise sentences, in chronological order, are the only thing they seem to understand.