Alex,
I had exactly the same problems with the water bills not being taken from my Spanish Bank Account. I completed in February 07. Last summer, I visited the water company, which is right at the top of one of the mountains! When I visited them, I gave them my account details and they started deducting the small water bills. There tel. no. is 952 47 67 84. In the details I got when I bought the apartment, they say to ask for Carmen. Also, they do speak English. Hope this helps.
Debbie