Eskom customer service non-existent

My pre-paid electricity meter packed up a three months ago, and Eskom replaced it with a new one. About a month and a half ago I made an electricity purchase, but accidentally used the old meter number. Due to this mistake, the voucher was not valid for the new meter, and I had to purchase another one. I tried to contact Eskom's client service line to arrange for a refund of the first purchase, or to convert it to a credit for the new meter, but it is seems impossible to get to speak to a consultant - I made numerous calls, but gave up every time after waiting for 20 minutes. I left messages three times for them to call me back, I sent 3 SMS's and I even wrote to them on their website. After a month and a half I have not received one call in reply to all the messages I sent. Eskom simply ignores all the channels they claim to have in place for customer interaction!