Poor service online

I am extremely disappointed with the poor service of shopping online with tfg I was purchasing a shoe from exact .. the first time around I placed an order, they cancelled my order ,when I phoned in to enquire the lady from the online customer services said that she cant do anything about it .. so I went online and selected the option for email me when available, a month later I saw that the size of the shoe I wanted was available but I had not received a single email telling me about that .. I placed an order again and they cancelled it yet again saying there is no stock availability.. if there is no stock then why do you keep showing it online ? .. this is the 3rd time that I am placing my order and if they cancel it again I am going to be extremely upset .. this is the worst experience I have had shopping online