Item at Local Distribution Center for too long

I recently purchased an item from the USA. Item was shipped through DHL mail. It arrived in RSA on the 21/01/18 and cleared at customs on the 25/01/18. It arrived at local distribution center on the 30/01/18. But when I call the post office (JHB international), they say the parcel is not in RSA and they cannot find it in their system. How does DHL tracking website locate the item, whereas Post office cannot locate the item. This is the tracking number (CG ********** 55DE) supp**** by the sender and DHL global.