Wrong Freezer

I went to the store on the 10/10/15 to buy a Defy or Kelvinator chest freezer. On the 13/10/15 a fridge star freezer was delivered, I immediately called the store and told Sandy the manager this is not what I asked for, its now been 5 weeks and I still don have the right freezer,Christmas is approaching and I will be having my children over and I can't buy anything, I haven't used the fridge star freezer but they are calling and sending letters to pay,I can't pay for something I don't have,I am a pensioner and have been going to the store regularly and all they say is they out of stock,I feel they are taking advantage, please help as I don't know what to do anymore.