Bad Service and inconsiderate

I have purchased a speaker, brand new and did not use it. I went back to the shop two days later for an exchange or refund and I was told that I should sell it to the shop as they only refund or exchange broken items. everything is still in tact nothing was done to it and when I resell it they offer me R150 for a speaker i purchased for R479. All I am asking is for an exchange or refund.