no help from Game N1 city

I was given as a present a kelvinator microwave in june and I have a 2 year garentee on it, it is now broken I took it back and was told they can not help me as I do not have a slip it was given as a present I went with my aunty to buy it and she does not have the slip anymore now Game N1 city will not help me. As far as I know all machine have serial numbers they should see on their system it was bought throu them. This is unacceptable and I would like someone to help me sort this issue out. How can they just send people away when they have a system to check if the item is theirs.