don't effin buy this

li
My bettas water heater quit working so today I went and bought a new one, $15 at Walmart. It didn't work, I figured I just got a crap one so I took it back and exchanged it. The one I exchanged it for doesn't work either. So now my betta just has to sit in chilly water until I a pet store opens tomorrow for me to buy a different brand. 
I'm extremely annoyed. So again fellow Betta owners, dont buy these because they do not fucking work. I'm taking it back tomorrow and getting my money back. The hell.