But they want my Credit Card + Bank Account No + Cellphone no. This is a link that was in the email. My first instinct was that this was a phishing email. Then when the link appeared genuine, I guessed its their way to discourage me from unsubscribing.

"I guessed its their way to discourage me from unsubscribing."

This is likely to be a new internet monetization scheme... Go ahead, mark this as spam, you'll never get another water utility bill again. To save money on your water bill, we send you these marketing messages every day.