Decofurn bed disaster

I tried a Sandhurst bed at 2 of their premises and were convinced that it was a medium firm bed. However when they delivered the bed it’s feels more like a extra firm bed and after sleeping on the bed for 2 nights I had to take Cataflam tablets due to aching neck/back. I went back to the store 2 days later. The manager came out to see the bed, agreed that the bed is firmer than the one on the floor and yet they still refuse to give me a refund!!! Unacceptable!!!