Torn plastic of packaging

I went and bought a Bed base cover for a queen sized bed at Alberton "New redruth pep home",only to find out that the packaging was wrong containing a double sized base cover. Then I went to exchange at Maponya Mall pep home, I was helped by Store manager who goes by the name Soso,she denied the exchange due to the wrapping of the package which was torn when I was opening the package, saying she can't accept it.