Mega Furniture Lied. They said my mattress would be there the next day and it wasn't, that it was on back order. Mesa Arizona

 I went to buy a mattress and was told it would be delivered to the store the next day.  When I went in to get it the next day, I was told that it was on back-order, and wouldn't be there until Wednesday.  I asked for a refund, and they said they didn't give refunds, that I had signed the invoice where it said there were no refunds.  I should have read the small print, but I thought I was signing an invoice stating I paid the bill and would be there the next day to pick it up.  I asked then if they could deliver it to me since it was there when it was supposed to be, and they said it was a $100 charge.  Today is Wednesday and I called to see if it was in, and it still is not.  The invoice says back orders could take 3-8 weeks.