This bill will probably be for the installation of your meter. I can't remember the exact amount but it was a fairly heavy fee. Since then bills are very reasonable. We use our place approx 15 weeks in the year and our most expensive quarterly bill for 2 of us has been about 35 euros.
The paperwork will likely be sitting in your post box in CDA but you can register to get these online at the office in Alhama next time you are here.