Issue With Amazon Return

This is regarding an order i placed on amazon ordered it on july 14 delivered it on july 24 delivered flip flops where different size one 10UK and one 8UK so i contacted amazon they told me that they will pick up the product from my home so waited about a month still no response so i contacted amazon again they told me that my return window is closed but after explaining it all to the executive he told me to shiip the product by myself so i shipped it to amazon after few days the consignment came back so i again contacted amazon again this time he told me that my return window closed so explained my situation then he told me to ship the product again and assured me that this time it will be over so i shipped it again and it came back again so i contacted amazon , they told me that the i will get the refund within 5 day and i waited about days and still no refund so i contacted amazon , they told me that its a bank issue and asked me to contact bank for further assistance i wish to file a dispute against amazon.What are my possibilities regarding this issue.