Walmart complaint: Expired Baby products sold

I went to Walmart (3255 Mission College Blvd, Santa Clara, CA 95054) to buy baby food. They keep it inside glass door and don’t let us see it unless we purchase. So, after waiting like 15 min by ringing the bell I went to find people to give me the formula that I needed. So, I fed it but then my baby fell sick and I investigated to find it was expired last year, even before my baby was born. Hence, I have been trying to complain about this. The store manager didn’t reply me when I filed online complain but just replaced all the expired ones. I went to the store to complain and he denied he has expired one (he replaced remaining expired ones after I complained). There is a video camera evidence and my bill and all can show he is lying and not doing his job properly. This is my second product from this store that is expired but it is serious baby formula and the way they keep it makes it so hard to catch date. I am very upset with this and attitude of your manager. If this is not addressed properly, I will take legal actions.