pathetic customer service wrong item was delivered

order number *** i order item from Leroy Merlin last month and they delivered a wrong braai stand i requested return and collection.they apologised for delivering wrong item and said item was mixed up yet they have not yet collected the wrong item i send them count less emails with no feedback .I will never ever buy online their customer service is pathetic today is the 10 September what must i do with a wrong item from August 15