Can’t exchange baby formula!!!

I really do not understand why I can’t exchange formula that I bought yesterday. I explained that I’m changing the brand due to dr advice. I was told that it’s policy as baby products are fragile...what’s the different between a tin of formula and that of coffee especially if it’s is still sealed. If other shops can exchange this product, clearly that explanation is ridiculous as it not a universal rule like underwear ???now what am I supposed to do with this milk???