Charging handling fee if they cannot deliver stock

On 25/05/2015 I ordered 3 parts from LG in Montague Gardens, they made me pay up front the amount of R460. A week later it was obvious they could not get the third of three parts, I asked them to try and my customer was willing to wait. Eventually my customer could not wait any longer and came to retrieve their broken microwave from me, this was on 15/05/2015, almost two months later. Bad bad service. They agreed to refund my money. I just received a refund from LG Montague Gardens for R390. R70 handling fee on something that they could not fullfill? come on, this is an outrage!!!!!