Failure to refund money

I bought five tickets for the 15:00 performance of the ballet, Snow White, at the Joburg Theatre on Sunday 15 October. I received the tickets from Pick ‘n Pay and paid the R1365 with my credit card. I subsequently wanted to change the date. On Monday 11 September I phoned Edgar Moagi ( ********** 898) at the theatre and he agreed to cancel the Sunday tickets and re-issue 5 tickets for Saturday 14 October at 15:00. He said he would credit my card for those tickets I had purchased and then deduct R1365 for the Saturday tickets. The latter transaction went through within minutes of my phone call but, to date, I have not been credited for the first set of tickets. I phoned him on Friday, 15 September, on Monday 18 September and on Friday 22 September, always in the morning. On the first two occasions I spoke to Mazipo who said Mr Moagi was not in but she would give him the message about the refund and he would phone me. On the third occasion, I got through to voice mail and left a message, asking about the refund. Edgar Moagi has never phoned me, nor has he put through the refund. I am a pensioner and cannot afford to 'donate' R1365 to the Jo'burg Theatre. What can I do to get my money back?