Lack of customer service

. I am writing to express my disappointment as I recently bought a wifi router during black Friday sale it was going for R200 at one of your mtn outlets in Cape Town strand street. Today I went there to return the router since I am not interested anymore and the router hasn't been opened it's still in the package but I was told there they cannot take it in because it's not faulty and I should sell it my self telling me I should know better before buying it there nothing they can do and the person who was assisting me was very rude.