I over paid and they do not want to pay me back.

I bought a dvd player at Alberton game store when I open it I found a cd and it gave me a lot problems from strange sounds coming out of it,I returned it back to the store and the service was bad I WAS blamed for not returning it sooner and the process of reversing my money back to me account took very long.As a game account holder I then took a loan at and they settled my game debt they paid extra money of which that extra money I informed Game about this and we reached an agreement that they will pay me back the money which was R900 plus the dvd player money which in all is R1500. As per our agreement they instructed me to fax my bank statement and my ID copy and I acted upon. I was told that they will pay me after 3 weeks it passed and still payment was not done.A week back I took a fridge with my game account when I went to the store to inquire about the delay of money that was supposed to be paid back to me I was told that as I took the fridge I owe them and the money that money which was supposed to be paid to me was paid as my instalment which was not our agreement and when purchasing the fridge I was never informed about this and also my instalment is not R1500