Bad service and no feedback

Three weeks ago I tried to use a voucher on the online app. It would not complete the transaction once payment was being made. After trying numerous times, I logged 2 complaints via email, of which neither has been answered to date. I then called the customer care line, I reported it four times. When I call again there is no record of the previous call. On Friday 29/8 I called again, logged a complaint again, and was told it would take 48 hours to get a response from IT. It is Tuesday afternoon 2/9. I called again. It is still hanging in the IT department with no response, no feed back & no way to use any voucher or promotion for the last 3 weeks. It is completely unacceptable and very bad service.