International Package stuck in transit ??

I was expecting a package ( EJ***ES ) from Spain to be delivered in Windhoek, Namibia. It left Spain the 15th of April (over the weekend) and arrived in SA on the 20th. It has since been there and that is all the information I have. The package contains very important documents which cost quite a lot both in terms of money and time to obtain. Further more, the UPU system shows South Africa as the destination. The phone numbers at Joburg International Mail Center never get answered. I really need those documents before end of next week and I don't know what to do.