[Selmavw]

The fact that the delivery company is saying that the weight was the same as when they sent it, doesn't prove anything.
There could be a problem with their packing.
There could be a slight deviation in weight when weighing the package. (4.5 grams is nothing)
Maybe in your case it is harder to claim that last point, because there were no other items in the package with a lot more weight.
I would recommend being persistent, because as far as you know, they have your money and you don't have the product.