I agreePersonally, I think you're stuffed!
I've never heard of two deposits being taken. I only take one and "hope" it covers everything - what a good idea though.
As you are not in Spain to argue the point, I don't think there is anything you can do about it now.
we moved out of our last place in September - by Xmas we were still being told that final bills hadn't come in - not that we believed that for a second
they were holding 1400€
in mid Jan we demanded to see bills & a final account - we knew there were several back bills for electricity & so on that we hadn't paid because they had never shown them to us - but we did expect to get something back
the final account shows that with 'repairs' the account balance was all of the 1400€ except about 3€
we have yet to see the bills for the repairs - even if they totally redecorated the place it couldn't have come to what they are claiming...........hmm might just chase that up