It's interesting cause I had a customer ask me that question, and my response was "you should be able to." And then another customer intercepted my answer and told the customer that they absolutely cannot and that they have to use cash. And that customer believed them.
I mean, even I was able to use my debit card for a WU money order at a different store. I asked a manager at my store if you could, and their response was yes.
I wonder why that other customer thought that you couldn't. Perhaps certain stores don't?