Dollar Tree

I purchased a can of condensed creamer and I was wanting condensed milk. I took it back in to exchange it and of course it being in a can it had not been opened. The cashier Andrea said I could not exchange a food item. I told her it did not say anthing on the receipt or that there was no sign stating you can't return food items. She said well you can't exchange it. If you can't return food items you all need to state this on your receipt or a sign in the store, because my receipt states "We will gladly exchange ANY UNOPENED item with the original receipt". So is this a true statement. I think someone who spends tons of money with you all should not be turned away by not letting you exchange something.