Refund not paid for - Its two months already

Hi, Hyundai Midrand made me pay for my 75km and 90km service while I was still covered by Liquid Capital. This came to my attention when Liquid capital called me to extend by cover from 90 KM. I follow up with Hyundai Midrand and specifically spoke to Mark. According to the records he could find he conceded for the 90KM incorrect service payment and confirmed that I will be refunded. As such, Hyundai Midrand promised to pay which they have not done since the beginning of December 2018. I was told because I use FNB, the amount should not take long to reflect after it’s finalised in that first week of December 2018. Notwithstanding the above concession, I remember vividly that I paid for my 75km service. I unfortunately lost my prove of payment. But I can give Hyundai Midrand my credit card detail to locate a payment that comes from it in their financial records for the same period. Nevertheless, I’ve since awaited an update but did not get it. I took it upon myself to follow-up both telephonically and in email. Whenever I call I am told that a follow-up will be done with Finance. They always promise to return feedback to me which they have never done. No one has ever called me or emails me irrespective of the number of telephonic and email follow ups I made and now we about to end the second Month. I was dealing specifically with Mark from the Services department. Can the Head Quarters please assist me, I bought my car brand new and I've always been ok until this event of poor service in both communicating with me for feedback and acting on my refund.