Don't use tnt global or express they want to be begged for their services

Hi I would like to lodge a complaint against TNT Global. I have been using their service for a year now ever since then my relationship hasn't been good, kept telling myself that no they will change not knowing that I am fooling myself they are the worst courier company ever to ship your stuff from China to South Africa. My stuff has been held up by customs for a week now, they have to send an email stating the reason why the stuff is held up and the way forward. Am I not the one calling and begging them to send me an invoice so I can clear and receive my stuff? Called their office and they put me on hold for 7 minutes then hanged up on me called them 5 times that's when they told me that their agent Kgosi who is supposed to assist me is not on his desk and I should called in 10 minutes time, asked to leave a message the person who answered I didn't get his name he said " hey hey mama he won't get back to you even if you left the message" that's totally unacceptable mind you it's really wrong. Now I must beg them to send me an invoice before they can release my stuff. Please help