Follow these simple rules:
Ring them one more time.
Wait for the usual flannel.
Tell them that if they don't get their a**es into gear you will be speaking to BALPA, IPA, Radio five live whoever.....that always does the trick.
Remember you are the customer and you deserve the respect not the other way round.Don't be afraid of making waves.....at least that way they know who you are.
Good luck ,but I bet you'll have to argue!