INCORRECT DATE ON ONLINE BOOKING-ANNOYED

I made a booking for a trip to Cape Town, in December, for my wedding anniversary. I fly on the 16th December - the return date was to be the 19th December - I did the booking on line, as with all my other bookings, I requested travel insurance as well, When I received a note from the insurers as the date of 19th Sept, I queried this with the insurance provider, this week, I call Mango, to confirm my times as the paperwork was at home, and I was advised that the return date was 19th September - how is this possible???? how can the system allow to leave on a date in December and return in September - I have made numerous calls to the client services, I was told to wait 48 hours, and each time I called I had to wait for 40 minutes to get through to someone - I still do not have an answer!!! this is my first holiday in 27 years with my husband, and Mango has just F@#!# it up!! I was advised not to book another flight for the 19th December until the IT dept investigates, but I still await - the manager Shubnam, gave me her direct line number, which just rings continuously, it saddens me, and I will never book Mango again!!!