Medexpress Discovery delivered incorrect medication

After several phone calls for incorrect medication delivery from medexpress, clicks...Discovery nothing is done, for collecting and deliver the correct medication. The delivery and invoice show July. 3 persons call me and still no one come back with the collection. My medical aid needs to be credited and correct medication delivered....what is not clear????? I want collection and correct medication delivered. The medical aid will not pay again. What should i do with the incorrect medication