Wrong Size Shirt

I ordered 3 size 3XL shirts. 2 of them are 100% but one is barely a size medium. I like the shirt that's the reason why I ordered it in the first place. When I was making enquires to replace the shirt, I was requested to send pictures of the shirt as well as pictures of bar codes. I am on vacation and it is not possible to send the requested pictures. I was offered some discount if I buy something else. What they don't understand...I WANT THE SHIRT... why would I order something that is 15 000 km away from me? The reason is simple...I like it. When receiving the wrong size, I really just want it to be replaced with the right size. But that seems to be a tall order.