Ball Fibre Duvet Inner Disaster

I bought a King size ball fibre duvet inner a while ago. Every second day the fibre shifts all the fibre to the sides leaving nothing in the middle so you freeze! And the sales person said Mr Price duvets are good quality it will not shift. Obviously this wasn't my first run in in with a duvet inner. But this inner costed me over R500 and I expected more. I like to shop at Mr Price. But I am really unhappy about this duvet and obviously I don't have the receipt although it should have a Mr Price label on it.