SAA completely useless

We are having endless problems with customer service today. We are travelling with our infant on 17 March 2015 and made a booking online, we called the call centre and they told us that we can't book for our infant online so we had to do it telephonically, they gave us a separate reference number for our baby. Now that we are trying to change our flight dates to 14 March at 10:05am, we are not allowed to, we called many times and they cut of our calls after us waiting for them to get information and most of all after 20 to 30 mins each call. Then they told us to go to the branch, we live in East London and we drove a long way from our home to sort it out since they didn't allow changes on our baby's flight online. When we get there at 5:26pm they were closed. This is not fair on customer. We also found that they booked our baby on a different class to us and now making it our fault since they charging us the same price as her flight just to change the date. We then tried calling again and the same thing happened, they don't even understand what they are doing at reservations and why is it our problem if we can't book infant flights online if your services don't allow it?, why