Disappointing On Line Service

Today I received an sms from Debonairs regarding an online special they are running until 12/3. "Buy 2 standard pizzas and get 1 free" I went online and placed my order, but when I went to checkout and inserted the voucher number it said invalid as voucher has expired". I phoned the call centre and was politely told that they could not help me but I should go back online and communicate via LIVE CHAT. I went back online but could not find the live chat any where. I phoned the call centre and told them my problem and they said they would transfer me directly to the store where I had placed the order. The phone rang, was picked up and promptly put down on me. I called again, line was engaged so I left a message. Waited but no response so I called back and again the line was engaged. I then phoned the call centre and asked to speak to the supervisor, I was put through to an extension where an answering machine asked me to leave a message which I did. I am still waiting for the supervisor, and the branch manager, to call me back. In the meantime my pizzas arrived and I ended up paying the full price for three standard sized pizzas. I would never have ordered these pizzas were it not for the special offer. I am very disappointed that not one of the call centre operators could assist. I doubt that I will use the online service again.