
Is it a brand new set or a second hand one? If it is brand new it will need programming either by an auto locksmith or vw garage. In most cases it isnt simply a straight forward swap unfortunately. You could try opening the key and swapping the chips over, but you risk damaging it which will cost you even more in the long run. If it is second hand then you will need to get a new key made for the chip to be programable.
HTH