What do you mean by detailed billing? I don't think I have itemised billing on my data contract as well. Can you imagine a long list of all the websites visited in a month. That could be a great service offering.
Are you getting "Due to routine system maintenance, no requests can be performed on MTN Active at this moment. Please contact MTNSP Customer Services (Dial 808 from an MTN Cellphone, or +27 83 1 808 from any other phone) to assist with this request. Alternatively, try again later."?