Walmart WIC cheese New York?

Recently my mother got custody of my 4 yr old neice and year old nephew. She recieves WIC checks. We've been able to use them at Shop Rites and other grocery stores without no other problems than just being unfamiliar with the items. At the other grocery stores she gets 16oz of deli cheese. Today at the Walmart deli they told her that Walmart does not have any cheese available for WIC, this does not make sense because she has always got the land o lakes american cheese. She got the cheese anyway and brought it to the register where they told her it wasn't WIC and that it was new regulations effective July 2010?! Does anyone have any idea about this? ((As with many Walmarts.... customer service or respect was not a priority))