customer is lying to get a refund. how do i have them return?

a customer ordered 4 items, claimed one of them was opened when it arrived (it wasn’t) and is saying he is uncomfortable eating the other 3 because one of them was opened. demanding a refund.

pretty obvious that he opened the first bag and is claiming it came like that to get a refund.

it is a food item so my question is how do i have him return the items back to me? it was about $70 total for all of them including the shipping cost so i’m really trying to fight this as i just got started doing this.