Waiting on payment

I am a member of Discovery and get paybacks each month when refuelling at BP. When I looked on the website this month I discovered that my qualifying amount is R0-00 even though I used BP and swiped the card. I phone Discovery only to be told that both my and my wife's card is apparently inactive - we have used the same cards for over a year now. I was told to resubmit the petrol slips which I did. Later the week I looked on the website and saw that some slips were picked up by Discovery but not all - even though I sent the ALL slips. I had to query it again (Discovery likes it when you need to guide them one step at a time). All were finally rectified but I was told that I would only be getting some of the cash now and only at the next cash run the rest. When I asked when this will be I was told between 10-15 December. This is totally unacceptable. What will Discovery do when I tell them I will only pay 70% of my contributions this month and the other maybe next month? Will Discovery pay me back the money with interest? I want the rest of the money this week still. I don't care whether you have certain systems or not. You certainly don't care when your members can't pay.