Poor Fast Freight delivery UPS

I have a business called Mans World in Walvis Bay Namibia. We have the DJI franchise and all our orders come with Express Air from China to us. It takes 4 to 6 days for delivery with DHL, Fedex, TNT etc. For some reason DJI decided to use UPS as well. What a nightmare. First delivery took about 10 days and I had to pay the import VAT upfront in spite of the fact that they have the VAT registration certificate. Now I am still waiting for a shipment sent from DJI on 06/07/2018 and my delivery date (changing all the time) now 25/07/2018. Three weeks. Also no real effort or valid explanation. Poooor service don't use them!!!