http://hellopeter.com/sa-post-office/complaints/parcel-held-up-at-jimc-1434959
Maybe do this tonight...
For Cape Town, they usually ask for the invoice showing the description and value of the goods, as well as the tracking number and instructions to fwd to your local PO. Also include your cell number.
Sometimes they may ask also for "proof of payment". This is usually an except from your credit card bill, you can black out all the other transactions and numbers.
Then follow up in a day or two, or check online to see if the item moved.