I've had a similar issue but with getting my refund for items they didn't have. Out of the 8 items ordered (on a most recent order) they only had 3 and it took a week to get a refund. I'm over Walmart and have moved on to a much better and cleaner grocery chain.
I would call the store and ask to speak with a CSR for food delivery and explain to them what's going on. Hopefully, they will resolve your issue ASAP.
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