Baby formula Return/Exchanges

So I have a question for anyone that may know why or know something about Walmart's return policies on baby formula. I bought 2 bottles of Enfamil ready made formula about 4 days ago. Today I opened it to give to my son. He absolutley hated it. I tried to take it back to Walmart and they told me they couldnt because it was their policy and the manager said no as well. Problem was they never showed me where in their policy it states this and the manager wouldnt even speak to me. Formula is expensive and to be told no when it comes to feeding a baby is frusterating. Has anyone else encountered this or knows what the policy is? Im so frusterated and my husband said we should being a lawsuit against them. I think that is a bit much, but I would appreciate some answers. Any help from you ladies is greatly appreciated!