Cameron at buliders warehouse in tokai treats customers like *********!

On the 29th June (between 9am-11am) my husband went to Builders in Tokai and purchased a 7kg gas bottle, a cooker top and a shower head. After paying for his items he realised that he had the wrong size gas bottle and he went straight to returns and received a credit note, went straight back into the store and took the 5kg bottle. (all this was done at till 2). He used my FNB card to pay for it, so I have the transaction on my bank statement. Since then we have realized it is still the wrong bottle and I called to find out if we can return the bottle and the cooker top. I was told we could. My husband took the bank statement as we don’t have the slip for the 5kg bottle and went to the store to have to refunded. When he got there is was told that they cannot find the 5kg bottle on record and therefore they won’t refund it! Cameron said he would do ‘his investigations’ and get back to us. We are still waiting, and it has been 4 days! He refunded the cooker top but refused to refund the gas bottle. My question is how is Cameron doing investigations when he took NO information or documentation from my husband? He thinks we are trying to ‘pull a move’ and he thinks if he says he’ll do investigations we’ll just go away because we are *********! Firstly, I don’t appreciate being treated like a ********, you wont refund because you think it is ******! check your camera footage! Secondly the fact that your processes do not account for the fact the 7kg bottle was already credited and now you can’t find this 5kg bottle on your records is not my problem! I now have a gas bottle that I cannot use and you are not being of any help at all. The gas bottle is in a perfectly sealed box with no damages!! I want my money back! And I will be sure in the future to take my business elsewhere. How do I get my money back from Builders warehouse in Tokai??