When I order there where in stock

Last week I ordered from Mr Price online. I bought a top for my son. It showed there were stock and payment went through. 2 Days later I got a email to tell me there were not enough stock and the had to refund his hoodie, but the rest of the items will be delivered. When I went to go look on the internet it showed there is still stock available. Now I have to order it again and pay delivery fees again and I feel this is not my problem because it shows there is stock available. I phoned the but Samantha Coopsamy can't give me an answer. I feel the are robbing me of another delivery fee.