How long does it take after registering as an independent student, to be able to apply online for exams?

How long does it take after registering as an independent student, to be able to apply online for exams? It has been already 3 working days since registering and I'm trying to apply myself for the writing paper exams of 11 Dec 2012, but the system reports that I have not any registered student services yet, although the payment has been already contacted the same time. I really don't want to pay twice the exam fee, and the email I've sent two days ago, has not been replied yet. :(