Locate my package, SA Post Office

I am a member of Manchester United Football Club. A package was sent from Manchester to my address in Cyrildene,

It was cleared by customs on the 12th of April, according to the tracking information, and has been awaiting my pickup since the 26th of April.

The post office code of ZA11438 is given, but not at which post office the package is being held. No delivery notice was delivered to my door. My email requesting the whereabouts of the package has not received a reply.

My fear is that in a day or two they will send the package back to England, even though they have not even notified me that it has arrived.