Abysmal customer service

On 15 February 2023, I assisted my sister-in-Law, who was returning to Thailand after many years in South Africa, to send a shipment of six (6) boxes of her personal belongings to Thailand. The boxes were sent from the Brits (0250) Post office and tracking numbers supp****. I have, since then, been trying to keep track of where the parcels are during their shipment to Thailand and have used e-mail and many phone calls to the Customer Services on ***. Who more often than not just do not answer their phones On 04 May 2023 I received a reply to one of my many e-mails informing me that the boxes were in transit to Thailand. This was also followed up by telephone, and I was told that they were still on the ship and expected to arrive by end May 2023. After trying to follow up again on Monday 19 June 2023 I received an e-mail on Tuesday 20 June informing me that one of the parcels could not be traced and that the remaining five (5) where still in South Africa. From the time of posing to today it is 18 Weeks. I need to locate all 6 boxes and get the expected delivery date to my Sister-in-Law in Thailand The service and the constant running from pillar to post with zero plausible information has now got me at the point of despair.