bed purchase from ikea

i saved up for weeks 2 buy a bed from ikea for my bedroom i bought a frame slats and mattress all seperate when purchasing i asked one of the assistants 4 guidance in buying this she told me what was best to purchase and the pick up point i then put everything through the till including bedside cabinets matching the bed and a childs bed i then questioned a lady that worked there that was dealing with till problems or complaints because it seemed to be more expensive than i imagined even though there was 10% off the malm range at the time i dont know whether that was for people just with the ikea family card or just anybody i left my receipt with this lady whilst we loaded our goods in the van i went back and collected my receipt she said there was no problem i accepted this my partner then assembled everything only to find the mattress was to big i cannot find my receipt and the frame has a chip in it i and my partner have rung them to no avail i understand they cannot change the mattress with no original packaging but they will not let us change the frame plus pay surplus for the bigger frame and slats with no receipt but they must have records from when they swiped my family card please is there anything you can do to help me i payed £500 plus for this bed and now im at the end of my tether as i have no bed to sleep in my partner is ok as he can sleep on one side but my side hangs other the frame we are both on benefits my partner has a bad back so he cannot work he also has dyslexia so thats why he approached the lady sales assisstant in the bedroom department we are now devastated it will take weeks to save and replace this