Substandard service and rude sales people

I bought a brand new Hyundai, October 2013 for my sister, she discovered that the license disc was expiring in July 2014 instead of October 2014. I went to them & presented the matter. They apologized & said I need a roadworthy test, they will then sort the disc registration and refund me. This was done in November 2014. I emailed the invoice R300 in early December and we are now in February 2015 and I still haven't received my refund. The person I was dealing with is Byron, and each time I phone there is story about the cheque needs be signed by the head office, or is not yet back from the head office. He had earlier on asked me to e-mail my bank details and proof of residence etc. which I did. Late January I phoned him again and he told me that he no longer works there. I asked who should I contact at the Glen to follow up and was given the name of Andre. First time I spoke to Andre he didn't know what I was talking about and he will phone Byron and come back to me. He never did, each time I phone him its one story or another, promise to give you feedback and they don't, and if you ask you are told the person is busy and you are not the only customer (that's what Andre said)