Spitz Does not Allow us to Return Snicker

Me and my Husband we bought a Snicker for R2 300 on the 29th of November 2019 at Spitz Cape Town Water Front. 07th November we went to Spitz to return the Snicker because it was small for my husband his feet was achong when he was wearing the Snicker. The lady by the name of Zimbini Kweneni told us that they cannot exchange the Snicker for us as we already used it. I dont understand because how could we know that the Snicker is small if we did not use it and mu husband wear that snicker once thats how he realised that the Snicker is too small for him. We cant let this go as R2g is more money to just let it go just like that. Please Help us Hello Peter. Contact *** or ***