Promised Exchanged

I bought me a Sneaker at sportscene Claremont, this date was October 2018, in Jan 2019 I returned it because the glue looked as it was coming loose. I was advise to where it until it breaks then return it, because the glue was loose at the time, however now that the glue is finally loose and the sneaker is open, I am told they cannot assist me with the exchange, firstly I only returned now because I was advised that the sneaker not broken I can only come when it breaks, I paid a lot of money, I don’t have account and have to safe up a very long time before I buy me a sneaker. I was told just keep the slip we will exchange it when you return . now no one wants to assist me with this sneaker. What must I now do