MTN doesn't give my 20GB once-off data

I've upgraded my phone a month ago. I didn't receive the 20GB once-off data which comes with an upgrade. I phoned the lady who assisted me, she didn't call me back. I called again the next day and she said she will log a query. She never did. Then on 5 July I called customer care and logged a query. They told me it will be resolved within 48 hours. Since then I've called another 3 times and every time I get the same answer. Nothing ever happens. My case was escalated as well and still after more tha a week, still nothing. It is easy - check my records and see that I didn't get my data and give me my data. In stead I have to follow up the whole time and every call takes 15 - 30 minutes as well. This is really ridiculous and I'm really frustrated by now!