Registered mail that cannot be tracked

I sent a registered letter on the 3rd December and it has just gone missing! The contact details they supply for you to phone them, ring constantly, telling you how important you are to them...but yet they never answer it. They also never answer emails that are sent to them. What is the point of registering a letter...you still have no guarantees it is going to arrive at its destination. Appalling service SAPO! This will be the next SOE that will end up going under business rescue!