first of all mate, this is a business transaction.. good will and youre feelings of a gesture will make you look as though you were aware of the fault at point of sale and by the letter of the law it will by purpose indicate that you signed fraudulently and so void the contract.
its their mistake and you need to focus on that and that alone, all feelings of right and wrong dont come into it. they miscalculated so someones getting a b0ll0cking more than likely so they will lean on you from all angles to resolve it.
honestly, you just need to close ranks dude, tell them you empathise with them but that empathy is all you can offer them, contracts are there to bind and protect both parties and you will be sheltering within that contract. There's nothing they can do about it, i dont even think they can legally chase you for it it either!