Samsung Fridge Freezer American Style?

I have had my Samsung Fridge Freezer American Style for about 6 years freezer is fine but late last year the water pipes in the fridge froze up then i could here the fan rubbing something then the back panel started to freez i took the back panel off which covers the elements and it was all froze up i have been defrosting it for the last 6/8 months every two weeks until i got in touch with a repair company who said they can repair it they said it is a common fault with then he said it was the polystyrene that had got water in ithe then put a new cover on it and said it should be `ok` now but 3 weeks later it is doing it again so he is coming back to it, ? do i get this extended warranty can some one let me know so it does not cost me any more money.