Goods swapped and replaced with low value goods

Terrible, Sent a parcel to Harare from Johannesburg with DHL Express South Africa on the 31st of May 2020. The estimated delivery date was the 8th of June 2020. After continuous daily complains about the delayed delivery, the parcel was received by the recipient on the 20th of June 2020 and they parcel had been switched. Reported the case immediately to both DHL South Africa and DHL Zimbabwe, 5days later they are saying we are still investigating