Incorrect Delivery twice!

On the 18.01.2016 i placed an order online, for some reason it would not let me checkout, i then called the customer service and was put through to the online department. I was told there is indeed stock of the 'Thermo Slim Waist Cincher\ SMALL size. I was advised that there is an issue with the online orders and i should try again in 20 minutes it should be fine. Indeed it was fixed when i logged back on and i could now checkout. I received delivery on the 23.01.2016. When i opened my delivery it was the WRONG size. i contacted the customer service department and was put through to a lady named Daniel who was apologetic and confirmed that she has arranged an exchange for Monday the 25th with the correct size. Its Monday the 25.01.2016 i received my delivery and AGAIN ITS THE WRONG SIZE. I call again only to be put on hold for 10 minutes. When i finally reach Daniel from the Online department she offers me another product and informs me that they do not have stock of the small size. Why was i told there was stock?? Why do you keep delivering the wrong size instead of informing the customer you are out of stock?? I expect a full refund & will no longer be making use of your service!"