I have to say that I am very happy to report that Blizzard have shown their better side today. Thanks to Kate at Blizzard customer support I will now get a refund for the last subscription. I am still unhappy with the original response I got but my confidence in Blizzard is restored well enough for me to become a loyal customer once again at their next game release.
I must add that I am a bit impressed by this turnaround. I had my mind set on receiving only silence from their side but this shows that the former trust definitely can be rebuilt.
Thanks Blizzard, and thanks Kate!