Lack of Service Delivery

I'm appalled with the lack of service delivery from the South African Post Office. A relatively urgent registered letter which was sent to me on 28 May 2015 was supposed to arrive at my address in Canada within 5 to 10 days. It has now been 18 days and when I checked the status of the letter on Domestic Track and Trace, I saw it is still sitting at JHB International Mail Centre! In fact, it took 5 days just to get the letter to the JHB International Mail Centre and it has been at this grossly inefficient mail centre for 13 days! This letter contained one document so no customs clearance is required. Can someone please explain to me why delivering one standard envelope containing one document by international airmail is so difficult? And also, what kind of service provider charges R75 to deliver a single standard envelope and fails to deliver within the specified timeframe? If we had known that the letter would still be sitting in SA after 18 days, we most certainly would have chosen to courier the letter using a different service provider. I will NOT be using the SA Post Office for any mail delivery in future and will spread the word of its gross inefficiency.