Being overcharged every month

I took out the Do Basic package for R399 per month.<br> <br> After 2 months I took a close look at my bill - only to find that I am being charged R450 per month!<br> <br> I raised the issue with the Call centre on the 18th of August. I was told that the 'discount' was not captured correctly.<br> To date nothing has been done, and I am still being charged the extra amount every month. <br> I keep on being told that the issue is being looked at - and it is with the \credit department' which has no telephone number