Builders Warehouse lacks refund etiquette...

Purchased a faulty generator from Builders Warehouse. Received appalling service from the sales manager. Returned it with a full tank of fuel. Store Manager has called to apologize and initiate the refund about a week ago. Builders head office sends me a letter to sign and send back and only once done will they give me R400. 00 as a good gesture!!! I filled the tank and was told by the sales manager that if I want the fuel, I should take it home and remove the petrol. I did not ask for any favors from Builders Warehouse but a Refund of the fuel that I put in. Why do I have to sign a settlement document for a refund. This experience has left a bad taste of Builderswarehouse. The most interesting part is that at the return counter is a board that states how Builderswarehouse will make sure that you as a customer will leave happy!