Refund problems after Mango can't honour my booking

I booked and paid for a flight to Cape Town Mango changed my departure times twice resulting in me having to keep changing my appointment times in Cape Town as well as changing car rental bookings Eventually I was forced to cancel my booking with Mango however they keep sending me messages that my flight has changed again I am also struggling to get my refund They don't reply to my emails and don't answer their phones