I agree with 170to5 and its just getting harder and harder to swap.
Put in an eswap then email the guy to briefly explain why you want the swap.
I don't even mind if the guy sends a text to my personal mobile (sent you an eswap)
If its rubbish for a good trip with no explanation, would anybody swap without an explanation.
I always reply yes or no to a swap request, so at least the guy can keep on trying and know where he or she stands.
We can at least respect the people we work with.