DSTV inefficient

I called last week to cancel my DSTV subscription (PVR and Extra View) but was advised that I need to call on 17 September, not one day before nor one day after, to cancel and that no other option is available. They are not able to process anything unless I call them on 17th September. If I miss that date and call on 18th September, then I need to wait another month and call on 17 October. Really?????<br> <br> I find this incredibly unbelievable and inefficient - why can I not cancel my subscription even if the notice period is a week or whatever. <br> <br> Please advise!