*** Sa Post office...where is my parcel!?

i have been expecting a parcel from the U.S for over a month now...the parcel was brought in through DHL ecommerce, the tracking number on the DHL wesite states that my parcel has arrived at customs on 23/03/2018....after continues calls to the post office(of which they never ever answer the phone) i finally get through to someone and they tell me that my parcel is not there....please tell me where my parcel is and when i can expect delivery, the problem is with the post office themselves as DHL can assure delivery on their part.