Originally MSC technical error - now my problem

I made a family booking online for a cruise in the March school holidays on my phone over the weekend. When I received confirmation via email the Monday I realised that the dates were incorrect. I contacted the call centre who was at that stage helpful in changing the dates, they offered alternate dates but I then had to change other bookings we made around our cruise and once done I contacted them. Then the booking we originally wanted was fully booked and the only other dates available is at twice the price for half the time. I keep calling and checking for available space on the cruise we want and spend at least half an hour explaining the whole situation all over again. Few months later, R3000 deposit and still no solution. If they cannot offer the cruise we originally booked, but due to technical error booked the incorrect one, now don't have space available, I want my deposit back and they refuse. There is no way of speaking to a senior, I end up with consultants who offers no solution after hours on the phone, there is also no alternative telephone numbers. I logged 2 email queries online as well - still no response!