Worst Customer Service I Have Ever Seen

Our company which is registered as an essential service provider ordered goods which arrived in South Africa on the 24th of April. they sent us the invoice to pay before release which had the incorrect customs tariff codes. we asked them to amend the invoice or credit and re-invoice us so we can pay and have the stock delivered. to date and after 40+ calls and over 10 emails we haven't been able to get correct paperwork for payment. this must be the worst customer service i have ever had to deal with in regards to a Courier and that is saying a lot. we have had bad service before (mostly due to the current Pandemic) but this takes it to a new level. I have never felt the need to write a review warning others away from a company until now.