Ignoring emails & changes time without consulation

I received a note out of the blue from FlySafair that my time of departure on 18 March 2016 (FA204) has been changed without consultation. It does not suit me. <br> I sent four emails for which I received three acknowledgements, but they do not come back to me.<br> If they cannot change my flight time back to the time that I booked, they must pay my money back.