Takealot even from a non profit organization!

I work for an NGO and we do presentations at schools when we distribute sponsored sanitary pads to Grade 7 girls. For this we need a projector screen as some of the schools we visit do not have screens available for us to use. I ordered a projector screen from Takealot only to discover after delivery and once we needed it, that it was way to big for us to transport. I logged a return and refund with Takealot. At no time during the return process was I notified that the item couldn't be returned. It was collected last week and I have now been informed that they won't accept the return, even though we have not made use of the screen at all, due to it being oversized. I subsequently ordered a smaller screen (which was a lot more expensive) thinking that the refund would cover the new smaller screen. What I don't understand is that Takealot will get a credit from their supplier for the returned item, while we must take the loss. I find this so unfair as the screen is brand new, all parts are in tacked including the packaging. Very disappointed in Takealot !!!!!! Taking a lot from an NGO!!!!!!