MRP Home Online not taking back incorrect item and refunding

Bought an item online which turned out not to be as described on the website (dimensions differed). After 2 calls to their helpdesk they told me the description was wrong and what I wanted they did not have. They first told me to return it to my nearest store for a refund but I asked what about the postage cost. They told me to claim that separately afterwards. I said no! This was their mistake and I don't see why I must follow 2 separate processes to get my money back. They then said they will send a courier to collect the item form me and refund me once they have it back. Almost 3 weeks later and numerous calls to their helpdesk and promises from their side, I still have the item and waiting for this courier to collect. I have given up. I will take the item to my nearest store and get a refund and then just write off the R70 postage I paid because if it's that difficult to get them to collect the item them its gonna be near impossible to get the full refund. Let this be a warning to anyone wanting to buy from MRP online - you can't trust their descriptions are 100% correct and as this example shows, it impossible to get them to take the item back and give a refund. This is my first and last time I buy from their website!