This place is a scam, they lie to get their salesman in your house even promise you gift cards that you never receive they pull soft credit reports as soon as they get your name and address by saying your getting a free water test that is rigged to make your water terrible then high pressure sales con you to buy the water system then they forget you and don't maintain it the people that own and run this business are crooks and this place needs to be shut down
As far as I can tell from the comments, it looks as though it's Florida Clean Energy & Water, Powered By The Sun, even though the caller id states "Unknown", and they leave no message.
I remember receiving these notifications in the mail in 2015 when my wife and I had purchased a home at the time. Since I pay a water bill each month, I'm pretty sure that's one of the methods they use in order to obtain phone numbers.
So far, they've called at least once a day within the past few days on my land line. Now that I have a call blocking device, they cannot get through.