Will WIC take my 4 unused cans of infant formula and reissue my voucher?

I just got issued 2 vouchers for Enfamil Infant but I have used 1 voucher. Now I believe my son may need to be on Enfamil Gentlease. I am going to see his pediatrician on Tuesday. If I need to switch his formula, will WIC take my unused cans and reissue a voucher for the one I used, or am I SOL. I live in California if that helps. I know each state has their own WIC policies. Enfamil products are used in California. Serious comments appreciated!