No delivery

I sent 2 parcels to my customer in Cape Town . They claim to have attempted delivery on the 4th but no call was received or anything . Till today they just redate the parcels and no delivery attempts or alerting the receiver of what’s happening. We tried to call no luck . Texted the WhatsApp number and even inboxed their Facebook page nothing . We are running businesses that relay on delivery on time and this is the worst service ever