Why does my North Carolina WIC voucher say I can get items that the store won't let me have?

For example: The voucher says "UP TO ONE POUND CHEESE" In the booklet that I got from the WIC department there are several varieties of cheese listed, sold in a variety of ways. At my local Food Lion they have tagged items displaying "WIC Approved Item" on only 2 items. When I got something that was listed in my booklet as being approved the cashier told me that it was only the marked items that I could get. I don't get it. Why would WIC approve an item and Food Lion not offer it as approved? I think its the same with the cereals. I did not see as many tagged as are on the list, though I know they carry at least a few of those. Does this happen at other stores? Do I need to just go to the manager?