Parcel Stuck at JIMC A

An overnight parcel was paid for and sent from the United Kingdom on 16 April 2020 for delivery to Cape Town. The item left the UK by air on 23 May 2020. The tracking number from Royal Mail is RZ622***267GB. As per the SA post track and trace function, the item only 'arrived' at the JIMC on June 15 2020. I have repeatedly tried to make contact with SA Post and the JIMC by email and phone to establish where in the network the item is with no success or response. I plead with you please to advise where my parcel is and when I can expect delivery?