15% Handling charge - Come on!!!

I purchased a Macbook Pro a week ago and was advised to get the Docking station because of the USB C ports. I purchased a recommended one from the sales guy without having a chance to have a look at what else was available. (I trusted he knew what he was talking about, But i dont think he would have picked it up) Turns out that this Docking station jams the wifi signal when i plug it in and i cannot use it with my Mac that i have just purchased. So i take the item back to the Pavillion store and return it. The returns guys gives me so much attitude and insist that there is a 15% handling charge. 1st of all, he had no idea what he was talking about when i explained my problem, and then told me "i should have asked the sales guy if it would jam my Wifi before i purchased it". So its my fault for not checking to see if the Docking station would cut the wifi signal. They seriously need a human that can speak to people better in that position. I dont wish for anyone to loose their job but maybe move him to another department where he doest deal with customers. I refused and I didn't pay the 15% handling charge and i received the full amount back thanks to the manage who stepped in and just authorised it without question. The thing that blows my mind... After spending R40 000 on a Macbook, they want to charge me 15% of R1699 handling fee for a product they recommended and sold me. F.Y.I returns guy. You buy a docking station to get your USB 3 to work with your USB C, Not to check Wifi signal. Dont think ill shop here again because of the "handling fee"