Bought gas and had to get a refund

Went into builders warehouse bought a carpet and a 9kg gas bottle. I Waited in the cold outside with my son for the gas bottle to be given to me then I get told its out of stock and I need to get a refund. I then Had to wait in the que for a refund and all I get is we are sorry. Then I had to wait 10min to get my money out of them. This is utterly pathetic service. How can management not communicate to staff that they are or of stock? My husband had to drive around in the parking lot while waiting me for me to get the refund sorted out. I currently want to return the carpet bought as well as I have never received such bad service from a store. This builders lost a very loyal customer now.