Sparkle Pool & Spa

I have yet to find a really stand out pool store in this area. Sparkle Pools has been my reluctant go-​to for chemicals and parts, but only because they are the closest to my house. My dad, who is the shop-​around type, has told me that their prices are a little steep. But still, they usually have what I need, and even when I’m not sure of a part’s name («uhh… it’s that rubbery black thingy that shaped kinda like a square and goes around the top of the black thing that you fill with water…»), they are able to help.
Today when I went in to get said rubbery black thingy, they handed me a package that had two inside. The woman ringing me up (who I believe is an owner or manager) asked me if I actually needed two of them, and when I said no, she ripped open the package and took one out. It was only after I got home that it occurred to me that she still charged me for both.
Maybe I should be giving myself two stars for not being assertive or motivated enough to drive back and complain, but instead, I’m giving them to Sparkle Pools for ripping me off. The point is, I shouldn’t HAVE to drive back and complain.