DSL Consumables - NOT HAPPY!

This company phoned us to say that because we took part in their survey they were going to send us a gift card and samples. This sample pack amounted to well below R200. When the samples came we realized they were 6 x 5L bottles and the Invoice was suddenly over R4000. When queried they said that the amount quoted over the phone was per liter which was not disclosed in the first place during the call. And we most certainly didn't expect samples to be bottles of 5L!! They refuse to take the products back and we refuse to pay the exuberant Invoice. I guess they will have to take us to court since there is no way of negotiating with them!