Missing packaging and instructions

We wanted to buy a heater and saw online that they had what we were after. On arriving there was only one left and it was on display. We asked for a box and instructions but after searching for some time they could not find either and told us to take it as is. We asked for a discount given the missing packaging and manual but they said no. Then a few days later we noticed a broad but shallow dent on the end of the unit. Even without the dent they should have offered a discount given the lack of packaging and manual. We still have not figured out all the functionality. But now with the dent they will hear from us again!